Magnetic field induced step-like changes in magnetization and resistivity of
SmSr manganites were studied. A strong dependence of these features on the
cooling rate was observed. Magnetostriction, however, does not show the
presence of large strain in our samples. From all these features we can rule
out the conventional explanation of magnetization jumps as a consequence of
martensitic transition. We propose instead that quenched by fast cooling
disorder leads to the formation of an inhomogeneous metastable state and to
subsequent magnetization jumps.Comment: 4 pages, 4 figures, to be published in PRB Brief

A. Aliev

A. V. Kalinov

C. Martin

D. I. Khomskii

H. Yoshizawa

I. F. Voloshin

J. Kushauer

L. M. Fisher

N. A. Babushkina

T. T. M. Palstra

Y. Tomioka

Y. Zhang

English

arXiv

Fisher, LM

Kalinov, AV

Voloshin, IF

Babushkina, NA

Khomskii, DI

Zhang, Y

Palstra, TTM

University of Groningen Research Database

  
 University of Groningen
Quenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3
Fisher, LM; Kalinov, AV; Voloshin, IF; Babushkina, NA; Khomskii, DI; Zhang, Y; Palstra,
Thomas
Published in:
Physical Review. B: Condensed Matter and Materials Physics
DOI:
10.1103/PhysRevB.70.212411
IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from
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2004
Link to publication in University of Groningen/UMCG research database
Citation for published version (APA):
Fisher, L. M., Kalinov, A. V., Voloshin, I. F., Babushkina, N. A., Khomskii, D. I., Zhang, Y., & Palstra, T. T.
M. (2004). Quenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3. Physical Review. B:
Condensed Matter and Materials Physics, 70(21), [212411]. DOI: 10.1103/PhysRevB.70.212411
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Quenched-disorder-induced magnetization jumps in Sm,SrMnO3
L. M. Fisher,1 A. V. Kalinov,1,2,* I. F. Voloshin,1 N. A. Babushkina,3 D. I. Khomskii,2,4 Y. Zhang,5 and T. T. M. Palstra2
1All-Russian Electrical Engineering Institute, 12 Krasnokazarmennaya Street, 111250 Moscow, Russia
2Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
3Institute of Molecular Physics, Russian Research Center “Kurchatov Institute,” Kurchatov Square 1, 123182 Moscow, Russia
4II Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
5Department of Physics, Leiden University, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands
(Received 29 July 2004; published 30 December 2004)
Magnetic field induced steplike changes in magnetization and resistivity of Sm1−xSrxMnO3 manganites were
studied. A strong dependence of these features on the cooling rate was observed. Magnetostriction, however,
does not show the presence of large strain in our samples. From all these features we can rule out the
conventional explanation of magnetization jumps as a consequence of martensitic transition. We propose
instead that quenched by fast cooling disorder leads to the formation of an inhomogeneous metastable state and
to subsequent magnetization jumps.
DOI: 10.1103/PhysRevB.70.212411 PACS number(s): 75.30.Kz, 71.30.1h, 75.47.Lx
Magnetic field-induced first order phase transitions attract
a lot of attention both in conventional antiferromagnets
(AFM)1 and in mixed-valence manganites (see Ref. 2 and
references therein) as well as in some pseudobinary
systems.3,4 In AFM these transitions are usually reversible
and relatively broad.1 In diluted metamagnets (for example,
FexMg1−xCl2) they may be steep (avalanchelike) and
hysteretic.5 In manganites such transitions may be sharp or
broad, reversible or strongly hysteretic6 depending on chemi-
cal composition and temperature, and are often accompanied
by structural and insulator-to-metal (I-M) transition.7–9
Recently, the field-induced phase transition to a ferromag-
netic (FM) state was shown to be discontinuous at low T
,5 K in ceramic Mn-doped Pr0.5Ca0.5MnO3,10,11 in ceramics
and single crystal of Pr1−xCaxMnO3 sx=0.3–0.37d12,13 and in
Gd5sSiGed4 alloys.3,4 The position and number of steps de-
pend on the magneto-temperature history and on the mag-
netic field sweep rate.3 This was interpreted as the result of
some kind of martensitic transformation. However, this sce-
nario is not clear because grain boundaries in ceramics could
be intrinsic barriers for domain-wall movement. Ghivelder et
al.14 have observed a huge temperature increase at such
abrupt field-induced transition (from 2.5 to 30 K), whereas
the specific heat before and after transition differs only by
10%. This implies that a large (magnetic) entropy is frozen in
the sample and abruptly released upon increase of the mag-
netic field. The authors of Ref. 14 have proposed a model in
which the local AFM-FM transition releases the heat locally
and triggers a heat avalanche leading to the observed mag-
netization jumps. In this case, the step should have some
finite characteristic time scale of the order of a thermal re-
laxation time. However, only the magnetic field width of the
step was discussed and was found to be less than 2 Oe12 or
even strictly zero.14
In this paper we show that steplike behavior exists in the
magnetization M and resistivity r but not in the magneto-
striction of Sm1−xSrxMn18O3 (x=0.45, 0.5) ceramics. These
steps have a characteristic time scale of the order of 1 ms
which does not depend on the magnetic field sweep rate.
Moreover, the low-field low-temperature magnetic state itself
strongly depends on the zero-field cooling rate. There are no
M and r steps for slowly s1 K/mind cooled samples, but
they exist only for rapidly cooled samples. In the latter case
there is an additional linear term in the specific heat vs tem-
perature dependence. We suggest that frozen magnetic disor-
der and corresponding entropy is responsible for the large
overheating at the avalanchelike transition to the FM state
upon increasing the magnetic field.
Ceramic Sm1−xSrxMn18O3 samples with x=0.45, 0.5 and
sNdEud0.55Sr0.45Mn18O3 were prepared by a solid-state reac-
tion technique, described in Ref. 15. The Nd/Eu ratio was
selected to fit the Sm ionic radius. The magnetic and electric
behavior of SmSr and (NdEu)Sr samples is qualitatively
identical [see Fig. 3(b)]. The enrichment of the samples by
18O was performed at T=950 °C and at a pressure p=1 bar
for 200 h using the method reported in Ref. 16. Magnetiza-
tion was measured by a Quantum Design MPMS-7 SQUID
magnetometer and by a vibrating sample magnetometer.
High-speed (up to 100 000 samplings per second) measure-
ments of the magnetization were performed using Fitz’s
technique and a fast analog-to-digital data acquisition board
(Data Translation). Resistivity, specific heat, and magneto-
striction were measured in PPMS-9 cryostat. To measure
magnetostriction we used WK-06-062AP-350 strain gauges
(Vishay Intertechnology) bonded to the sample with a proper
epoxy. The striction was detected by the change in resistance
of the strain gauge.
Sm1−xSrxMnO3 with x<0.5 is known to be in the vicinity
of the I-M and AFM-FM transition.17 So, for this system the
electronic and magnetic state can be tuned by the application
of a magnetic field or by oxygen-isotope substitution.
Sm0.5Sr0.5Mn18O3 is an insulator in the low-temperature
ground state, and undergoes an I-M transition after 18O-to-
16O substitution, after reduction of the doping level to x
=0.45, or under application of the magnetic field of the order
of 1 T.18 Our magnetization data (Fig. 1) show that there are
PHYSICAL REVIEW B 70, 212411 (2004)
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two types of field-induced transition for 18O samples: at low
temperatures there appears an irreversible transition from an
AFM to FM state, and at high temperatures T.Tc—a revers-
ible albeit slightly hysteretic PM-FM transition. Magneto-
striction of about 2310−4 is clearly seen to accompany the
PM-FM transition (upper inset) in accordance with the data
of Ref. 19. The 1/x data just above Tc show a tendency for
AFM interactions that competes with FM ordering at inter-
mediate temperatures.
The irreversible metamagnetic AFM-FM transition is
shown to be steplike (Fig. 2) after zero-field cooling. We
have observed that the step location depends on the sweep
rate of the following magnetic field: the smaller the sweep
rate, the larger the field value needed to realize the transition.
For the Sm0.5Sr0.5Mn18O3 sample at the rate ł250 Oe/s the
transition becomes smooth. This shows that the steplike tran-
sition is not an intrinsic property of a compound. Two ques-
tions arise at this point: (i) how sharp are these steps and (ii)
is M a function of the magnetic field along all the steps or is
only the start of the transition triggered by the magnetic
field?
To resolve these problems we have studied the MsHd
steps at different sweep rates with our high-speed experimen-
tal setup with 10 ms resolution. The results shown in the
inset to Fig. 2 demonstrate the finite width of the transition
of the order of 1 ms. Note that this curve is the same for
different sweep rates s200–3000 Oe/sd. Being triggered, the
transition will complete in a definite time independent on the
further changes of the H. In the case of Sm0.5Sr0.5Mn18O3,
this time scale is approximately 10 times higher (not shown).
Thus, our samples with a relatively small difference in Sr
content exhibit a factor of 10 difference in the transition
time. This fact cannot be easily reconciled with the scenario
of a martensitic transition because the microstructure of both
samples is identical. Moreover, a distribution of avalanches
in martensitic transformations has usually no characteristic
time scales20 unlike our observations.
To further elucidate the origin of such sharp transitions,
we have checked the effects of the cooling rate on the low-
temperature magnetic state (Fig. 3). The quenched-in disor-
der should be strongly affected by the cooling rate. In the
case of martensitic transformation,20 a slow cooling rate
leads to a low defect concentration so that the strains are
released via large avalanches. On the other hand, fast cooling
results in a large number of defects and thus leads to a se-
quence of many small avalanches. However, as we will dis-
cuss below, the behavior observed in our experiments with
different cooling rates shows the opposite tendency. This is
in our opinion a strong argument against the interpretation of
the jumps as a consequence of martensitic phenomena.
Two cooling rates were used in our experiments. In the
first, slow cooling, the sample was cooled at the rate of
1 K/min from 300 K to 5 K in zero applied field for trans-
port and specific heat measurements and 100 Oe for magne-
tization experiments. In the second, fast cooling regime, the
cooling rate was 10 K/min for resistivity and specific heat
measurements and approximately 20 K/min for magnetiza-
tion. Usually, no specific information is provided in the lit-
erature on the employed cooling rate in manganite research,
and we assume that most results are obtained using a rela-
tively fast cooling rate.
Two key points should be noted in the data of Fig. 3. The
first is a huge thermal hysteresis for the data obtained on
heating and cooling, which is generally considered to be a
fingerprint of a first order phase transition. The second is a
striking difference in the low-temperature states of the
FIG. 1. Magnetization loops for Sm0.55Sr0.45MnO3 recorded af-
ter zero-field cooling from room temperature. The data for the first
increase of the magnetic field are shown in the first quadrant and
marked with bold arrows if different from stable curves (III quad-
rant). T=5 K (h), 55 K (s), 120 K (n), and 140 K (,). The upper
left inset shows magnetostriction at 120 K, the lower right one pre-
sents a high-temperature tail of inverse susceptibility at m0H
=0.1 T.
FIG. 2. The dependence of the magnetization jump on the mag-
netic field sweep rate for Sm0.55Sr0.45Mn18O3 (a) and
Sm0.5Sr0.5Mn18O3 (b) at T=5 K. Inset shows the time dependence
of the magnetization during the jump. This dependence is the same
for the sweep rates in the range 200–3000 Oe/s.
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fast- and slow-cooled samples. For the former, we observe a
low-magnetization state with a relatively high resistivity. For
the latter, the magnetization is 10 times higher and the resis-
tivity is smaller. The additional linear term in the specific
heat appears for the fast cooled sample as shown in the inset
to Fig. 3(a). These differences diminish upon heating and
disappears at T<45 K.
The low-temperature magnetization and resistivity loops
after slow and fast cooling (Fig. 4) have qualitatively differ-
ent behavior. The steplike transition in MsHd and rsHd exists
only for fast cooled samples, whereas this transformation is
smooth in slow cooled samples. Comparison of the data of
Figs. 4(a) and 4(b) shows that the fast-cooled samples have
significantly larger resistivity even at the same value of M
[compare, for instance, rsH=0.5,1.1 Td]. This is an evidence
for a quenched disorder in fast-cooled samples (cf. Ref. 21).
The other evidence of an additional disorder is shown in the
inset to Fig. 3(a). The fitting of the temperature dependence
of the specific heat is the same for both cooling rates except
an additional linear term of the order of 20% in the fast-
cooled sample. (Note, that conductivity in this case is even
lower and the electron term could not be the origin of this
change.) Corresponding extra entropy DS=0.25 J /K/mol is
of the same order as the entropy change upon PM-FM tran-
sition s,0.6 J /K/mold, thus we believe this extra linear term
to have essentially magnetic origin, possibly spin-glass-like
type.22 However, there is almost no additional strain (less
than 10−5) in the fast-cooled sample and the magnetostriction
is smooth for both histories. This, together with the opposite
dependence of the behavior of our samples on the cooling
rate, mentioned above, in our opinion rules out the descrip-
tion of these phenomena as a consequence of a martensitic
nature of the transition.
Upon cooling, the AFM-FM competition may result in a
strongly disordered magnetic state, which has an excess spe-
cific heat and enhanced magnetocaloric effect.23 Ferromag-
netic ordering with the external magnetic field would lead to
the reduction of this extra entropy. In this case, the local
release of the frozen entropy may result in the avalanchelike
overheating of the sample because the higher the temperature
the more tendency to ferromagnetism is observed at low tem-
peratures (cf. the data for 5 and 55 K in Fig. 1). So, both the
magnetization and resistivity change in a jumplike fashion.
Such effect was observed recently14 on the steplike transi-
tion. This scenario assumes the time scale of the transition to
be inversely proportional to the thermal conductivity of the
sample. This is exactly the case if one compares
Sm1−xSrxMn18O3 with x=0.45 and 0.5. The resistivity of
Sm0.5Sr0.5Mn18O3 is at least four orders of magnitude
higher18 so that the thermal conductivity should be lower. We
recall that the observed time scale of the jump for
Sm0.5Sr0.5Mn18O3 is 10 times larger than for
Sm0.55Sr0.45Mn18O3.
Summarizing, we studied the magnetization and resistiv-
ity jumps in Sm1−xSrxMn18O3, especially their dependence
on the cooling rate. The slow s1 K/mind cooled samples
demonstrate a smooth AFM-FM transition upon increase of
the magnetic field, in contrast to the fast s,10 K/mind
cooled samples where this transition is steplike with a char-
acteristic time scale of 1 ms. The results obtained (the
FIG. 3. The temperature dependences of the low-field s0.01 Td
magnetization (a) and zero-field resistivity (b) of
Sm0.55Sr0.45Mn18O3 obtained for different temperature histories:
(s) slow cooling, (P) heating after slow cooling, and (n) heating
after fast cooling. Insets show the temperature dependence of the
specific heat (a) and resistivity (b) of sNdEud0.55Sr0.45Mn18O3 for
the same temperature histories.
FIG. 4. Magnetization (a) and resistivity (b) loops for
Sm0.55Sr0.45Mn18O3 recorded at 5 K after slow and fast cooling in
zero field, which demonstrate the absence of jumps for slowly
cooled samples. The inset shows a minor effect of the cooling rate
on the magnetostriction. Here the parabolic increase is caused by
the magnetoresistance of the gauge itself.
BRIEF REPORTS PHYSICAL REVIEW B 70, 212411 (2004)
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dependence of the jumps on the cooling rate; the constant
time scale of the jumps, independent on the field-sweep rate;
the behavior of specific heat; the absence of noticeable mag-
netostriction) disagree with the often used interpretation that
the magnetization steps originate from the strain release at a
martensitic transition. We suggest that the frozen disorder
and the associated entropy is the origin of an excess specific
heat which is released in an avalanchelike way upon apply-
ing a magnetic field, resulting in a heat burst in the sample
and in steps in the magnetization and resistivity.
This study was supported by the Netherlands Organiza-
tion for the Advancement of Pure Research (NWO) and IN-
TAS project (01-2008).
*Corresponding author. Email address: kalinov@vei.ru
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BRIEF REPORTS PHYSICAL REVIEW B 70, 212411 (2004)
212411-4


Quenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3

University of Groningen

   University of GroningenQuenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3Fisher, LM; Kalinov, AV; Voloshin, IF; Babushkina, NA; Khomskii, DI; Zhang, Y; Palstra, TTMPublished in:Physical Review. B: Condensed Matter and Materials PhysicsDOI:10.1103/PhysRevB.70.212411IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2004Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Fisher, LM., Kalinov, AV., Voloshin, IF., Babushkina, NA., Khomskii, DI., Zhang, Y., & Palstra, TTM. (2004).Quenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3. Physical Review. B: Condensed Matterand Materials Physics, 70(21), [212411]. https://doi.org/10.1103/PhysRevB.70.212411CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 12-11-2019Quenched-disorder-induced magnetization jumps in Sm,SrMnO3L. M. Fisher,1 A. V. Kalinov,1,2,* I. F. Voloshin,1 N. A. Babushkina,3 D. I. Khomskii,2,4 Y. Zhang,5 and T. T. M. Palstra21All-Russian Electrical Engineering Institute, 12 Krasnokazarmennaya Street, 111250 Moscow, Russia2Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands3Institute of Molecular Physics, Russian Research Center “Kurchatov Institute,” Kurchatov Square 1, 123182 Moscow, Russia4II Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany5Department of Physics, Leiden University, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands(Received 29 July 2004; published 30 December 2004)Magnetic field induced steplike changes in magnetization and resistivity of Sm1−xSrxMnO3 manganites werestudied. A strong dependence of these features on the cooling rate was observed. Magnetostriction, however,does not show the presence of large strain in our samples. From all these features we can rule out theconventional explanation of magnetization jumps as a consequence of martensitic transition. We proposeinstead that quenched by fast cooling disorder leads to the formation of an inhomogeneous metastable state andto subsequent magnetization jumps.DOI: 10.1103/PhysRevB.70.212411 PACS number(s): 75.30.Kz, 71.30.1h, 75.47.LxMagnetic field-induced first order phase transitions attracta lot of attention both in conventional antiferromagnets(AFM)1 and in mixed-valence manganites (see Ref. 2 andreferences therein) as well as in some pseudobinarysystems.3,4 In AFM these transitions are usually reversibleand relatively broad.1 In diluted metamagnets (for example,FexMg1−xCl2) they may be steep (avalanchelike) andhysteretic.5 In manganites such transitions may be sharp orbroad, reversible or strongly hysteretic6 depending on chemi-cal composition and temperature, and are often accompaniedby structural and insulator-to-metal (I-M) transition.7–9Recently, the field-induced phase transition to a ferromag-netic (FM) state was shown to be discontinuous at low T,5 K in ceramic Mn-doped Pr0.5Ca0.5MnO3,10,11 in ceramicsand single crystal of Pr1−xCaxMnO3 sx=0.3–0.37d12,13 and inGd5sSiGed4 alloys.3,4 The position and number of steps de-pend on the magneto-temperature history and on the mag-netic field sweep rate.3 This was interpreted as the result ofsome kind of martensitic transformation. However, this sce-nario is not clear because grain boundaries in ceramics couldbe intrinsic barriers for domain-wall movement. Ghivelder etal.14 have observed a huge temperature increase at suchabrupt field-induced transition (from 2.5 to 30 K), whereasthe specific heat before and after transition differs only by10%. This implies that a large (magnetic) entropy is frozen inthe sample and abruptly released upon increase of the mag-netic field. The authors of Ref. 14 have proposed a model inwhich the local AFM-FM transition releases the heat locallyand triggers a heat avalanche leading to the observed mag-netization jumps. In this case, the step should have somefinite characteristic time scale of the order of a thermal re-laxation time. However, only the magnetic field width of thestep was discussed and was found to be less than 2 Oe12 oreven strictly zero.14In this paper we show that steplike behavior exists in themagnetization M and resistivity r but not in the magneto-striction of Sm1−xSrxMn18O3 (x=0.45, 0.5) ceramics. Thesesteps have a characteristic time scale of the order of 1 mswhich does not depend on the magnetic field sweep rate.Moreover, the low-field low-temperature magnetic state itselfstrongly depends on the zero-field cooling rate. There are noM and r steps for slowly s1 K/mind cooled samples, butthey exist only for rapidly cooled samples. In the latter casethere is an additional linear term in the specific heat vs tem-perature dependence. We suggest that frozen magnetic disor-der and corresponding entropy is responsible for the largeoverheating at the avalanchelike transition to the FM stateupon increasing the magnetic field.Ceramic Sm1−xSrxMn18O3 samples with x=0.45, 0.5 andsNdEud0.55Sr0.45Mn18O3 were prepared by a solid-state reac-tion technique, described in Ref. 15. The Nd/Eu ratio wasselected to fit the Sm ionic radius. The magnetic and electricbehavior of SmSr and (NdEu)Sr samples is qualitativelyidentical [see Fig. 3(b)]. The enrichment of the samples by18O was performed at T=950 °C and at a pressure p=1 barfor 200 h using the method reported in Ref. 16. Magnetiza-tion was measured by a Quantum Design MPMS-7 SQUIDmagnetometer and by a vibrating sample magnetometer.High-speed (up to 100 000 samplings per second) measure-ments of the magnetization were performed using Fitz’stechnique and a fast analog-to-digital data acquisition board(Data Translation). Resistivity, specific heat, and magneto-striction were measured in PPMS-9 cryostat. To measuremagnetostriction we used WK-06-062AP-350 strain gauges(Vishay Intertechnology) bonded to the sample with a properepoxy. The striction was detected by the change in resistanceof the strain gauge.Sm1−xSrxMnO3 with x<0.5 is known to be in the vicinityof the I-M and AFM-FM transition.17 So, for this system theelectronic and magnetic state can be tuned by the applicationof a magnetic field or by oxygen-isotope substitution.Sm0.5Sr0.5Mn18O3 is an insulator in the low-temperatureground state, and undergoes an I-M transition after 18O-to-16O substitution, after reduction of the doping level to x=0.45, or under application of the magnetic field of the orderof 1 T.18 Our magnetization data (Fig. 1) show that there arePHYSICAL REVIEW B 70, 212411 (2004)1098-0121/2004/70(21)/212411(4)/$22.50 ©2004 The American Physical Society212411-1two types of field-induced transition for 18O samples: at lowtemperatures there appears an irreversible transition from anAFM to FM state, and at high temperatures T.Tc—a revers-ible albeit slightly hysteretic PM-FM transition. Magneto-striction of about 2310−4 is clearly seen to accompany thePM-FM transition (upper inset) in accordance with the dataof Ref. 19. The 1/x data just above Tc show a tendency forAFM interactions that competes with FM ordering at inter-mediate temperatures.The irreversible metamagnetic AFM-FM transition isshown to be steplike (Fig. 2) after zero-field cooling. Wehave observed that the step location depends on the sweeprate of the following magnetic field: the smaller the sweeprate, the larger the field value needed to realize the transition.For the Sm0.5Sr0.5Mn18O3 sample at the rate ł250 Oe/s thetransition becomes smooth. This shows that the steplike tran-sition is not an intrinsic property of a compound. Two ques-tions arise at this point: (i) how sharp are these steps and (ii)is M a function of the magnetic field along all the steps or isonly the start of the transition triggered by the magneticfield?To resolve these problems we have studied the MsHdsteps at different sweep rates with our high-speed experimen-tal setup with 10 ms resolution. The results shown in theinset to Fig. 2 demonstrate the finite width of the transitionof the order of 1 ms. Note that this curve is the same fordifferent sweep rates s200–3000 Oe/sd. Being triggered, thetransition will complete in a definite time independent on thefurther changes of the H. In the case of Sm0.5Sr0.5Mn18O3,this time scale is approximately 10 times higher (not shown).Thus, our samples with a relatively small difference in Srcontent exhibit a factor of 10 difference in the transitiontime. This fact cannot be easily reconciled with the scenarioof a martensitic transition because the microstructure of bothsamples is identical. Moreover, a distribution of avalanchesin martensitic transformations has usually no characteristictime scales20 unlike our observations.To further elucidate the origin of such sharp transitions,we have checked the effects of the cooling rate on the low-temperature magnetic state (Fig. 3). The quenched-in disor-der should be strongly affected by the cooling rate. In thecase of martensitic transformation,20 a slow cooling rateleads to a low defect concentration so that the strains arereleased via large avalanches. On the other hand, fast coolingresults in a large number of defects and thus leads to a se-quence of many small avalanches. However, as we will dis-cuss below, the behavior observed in our experiments withdifferent cooling rates shows the opposite tendency. This isin our opinion a strong argument against the interpretation ofthe jumps as a consequence of martensitic phenomena.Two cooling rates were used in our experiments. In thefirst, slow cooling, the sample was cooled at the rate of1 K/min from 300 K to 5 K in zero applied field for trans-port and specific heat measurements and 100 Oe for magne-tization experiments. In the second, fast cooling regime, thecooling rate was 10 K/min for resistivity and specific heatmeasurements and approximately 20 K/min for magnetiza-tion. Usually, no specific information is provided in the lit-erature on the employed cooling rate in manganite research,and we assume that most results are obtained using a rela-tively fast cooling rate.Two key points should be noted in the data of Fig. 3. Thefirst is a huge thermal hysteresis for the data obtained onheating and cooling, which is generally considered to be afingerprint of a first order phase transition. The second is astriking difference in the low-temperature states of theFIG. 1. Magnetization loops for Sm0.55Sr0.45MnO3 recorded af-ter zero-field cooling from room temperature. The data for the firstincrease of the magnetic field are shown in the first quadrant andmarked with bold arrows if different from stable curves (III quad-rant). T=5 K (h), 55 K (s), 120 K (n), and 140 K (,). The upperleft inset shows magnetostriction at 120 K, the lower right one pre-sents a high-temperature tail of inverse susceptibility at m0H=0.1 T.FIG. 2. The dependence of the magnetization jump on the mag-netic field sweep rate for Sm0.55Sr0.45Mn18O3 (a) andSm0.5Sr0.5Mn18O3 (b) at T=5 K. Inset shows the time dependenceof the magnetization during the jump. This dependence is the samefor the sweep rates in the range 200–3000 Oe/s.BRIEF REPORTS PHYSICAL REVIEW B 70, 212411 (2004)212411-2fast- and slow-cooled samples. For the former, we observe alow-magnetization state with a relatively high resistivity. Forthe latter, the magnetization is 10 times higher and the resis-tivity is smaller. The additional linear term in the specificheat appears for the fast cooled sample as shown in the insetto Fig. 3(a). These differences diminish upon heating anddisappears at T<45 K.The low-temperature magnetization and resistivity loopsafter slow and fast cooling (Fig. 4) have qualitatively differ-ent behavior. The steplike transition in MsHd and rsHd existsonly for fast cooled samples, whereas this transformation issmooth in slow cooled samples. Comparison of the data ofFigs. 4(a) and 4(b) shows that the fast-cooled samples havesignificantly larger resistivity even at the same value of M[compare, for instance, rsH=0.5,1.1 Td]. This is an evidencefor a quenched disorder in fast-cooled samples (cf. Ref. 21).The other evidence of an additional disorder is shown in theinset to Fig. 3(a). The fitting of the temperature dependenceof the specific heat is the same for both cooling rates exceptan additional linear term of the order of 20% in the fast-cooled sample. (Note, that conductivity in this case is evenlower and the electron term could not be the origin of thischange.) Corresponding extra entropy DS=0.25 J /K/mol isof the same order as the entropy change upon PM-FM tran-sition s,0.6 J /K/mold, thus we believe this extra linear termto have essentially magnetic origin, possibly spin-glass-liketype.22 However, there is almost no additional strain (lessthan 10−5) in the fast-cooled sample and the magnetostrictionis smooth for both histories. This, together with the oppositedependence of the behavior of our samples on the coolingrate, mentioned above, in our opinion rules out the descrip-tion of these phenomena as a consequence of a martensiticnature of the transition.Upon cooling, the AFM-FM competition may result in astrongly disordered magnetic state, which has an excess spe-cific heat and enhanced magnetocaloric effect.23 Ferromag-netic ordering with the external magnetic field would lead tothe reduction of this extra entropy. In this case, the localrelease of the frozen entropy may result in the avalanchelikeoverheating of the sample because the higher the temperaturethe more tendency to ferromagnetism is observed at low tem-peratures (cf. the data for 5 and 55 K in Fig. 1). So, both themagnetization and resistivity change in a jumplike fashion.Such effect was observed recently14 on the steplike transi-tion. This scenario assumes the time scale of the transition tobe inversely proportional to the thermal conductivity of thesample. This is exactly the case if one comparesSm1−xSrxMn18O3 with x=0.45 and 0.5. The resistivity ofSm0.5Sr0.5Mn18O3 is at least four orders of magnitudehigher18 so that the thermal conductivity should be lower. Werecall that the observed time scale of the jump forSm0.5Sr0.5Mn18O3 is 10 times larger than forSm0.55Sr0.45Mn18O3.Summarizing, we studied the magnetization and resistiv-ity jumps in Sm1−xSrxMn18O3, especially their dependenceon the cooling rate. The slow s1 K/mind cooled samplesdemonstrate a smooth AFM-FM transition upon increase ofthe magnetic field, in contrast to the fast s,10 K/mindcooled samples where this transition is steplike with a char-acteristic time scale of 1 ms. The results obtained (theFIG. 3. The temperature dependences of the low-field s0.01 Tdmagnetization (a) and zero-field resistivity (b) ofSm0.55Sr0.45Mn18O3 obtained for different temperature histories:(s) slow cooling, (P) heating after slow cooling, and (n) heatingafter fast cooling. Insets show the temperature dependence of thespecific heat (a) and resistivity (b) of sNdEud0.55Sr0.45Mn18O3 forthe same temperature histories.FIG. 4. Magnetization (a) and resistivity (b) loops forSm0.55Sr0.45Mn18O3 recorded at 5 K after slow and fast cooling inzero field, which demonstrate the absence of jumps for slowlycooled samples. The inset shows a minor effect of the cooling rateon the magnetostriction. Here the parabolic increase is caused bythe magnetoresistance of the gauge itself.BRIEF REPORTS PHYSICAL REVIEW B 70, 212411 (2004)212411-3dependence of the jumps on the cooling rate; the constanttime scale of the jumps, independent on the field-sweep rate;the behavior of specific heat; the absence of noticeable mag-netostriction) disagree with the often used interpretation thatthe magnetization steps originate from the strain release at amartensitic transition. We suggest that the frozen disorderand the associated entropy is the origin of an excess specificheat which is released in an avalanchelike way upon apply-ing a magnetic field, resulting in a heat burst in the sampleand in steps in the magnetization and resistivity.This study was supported by the Netherlands Organiza-tion for the Advancement of Pure Research (NWO) and IN-TAS project (01-2008).*Corresponding author. Email address: kalinov@vei.ru1 E. Stryjewski and N. Giordano, Adv. Phys. 26, 487 (1977).2 J. M. D. Coey, M. Viret, and S. von Molnár, Adv. Phys. 48, 167(1999).3 V. Hardy et al., Phys. Rev. B 69, 020407(R) (2004).4 E. M. Levin, K. A. Gschneidner, Jr., and V. K. Pecharsky, Phys.Rev. B 65, 214427 (2002).5 J. Kushauer, R. van Bentum, W. Kleemann, and D. Bertrand,Phys. Rev. B 53, 11 647 (1996).6 G. Xiao, G. Q. Gong, C. L. Canedy, E. J. McNiff, Jr., and A.Gupta, J. Appl. Phys. 81, 5324 (1997).7 Y. Tomioka, A. Asamitsu, Y. Moritomo, H. Kuwahara, and Y.Tokura, Phys. Rev. Lett. 74, 5108 (1995).8 Y. Tomioka, A. Asamitsu, H. Kuwahara, Y. Moritomo, and Y.Tokura, Phys. Rev. B 53, R1 689 (1996).9 H. Yoshizawa, H. Kawano, Y. Tomioka, and Y. Tokura, Phys.Rev. B 52, R13 145 (1995).10 S. Hébert, A. Maignan, V. Hardy, C. Martin, M. Hervieu, B.Raveau, R. Mahendiran, and P. Schiffer, Eur. Phys. J. B 29, 419(2002).11 S. Hébert, A. Maignan, V. Hardy, C. Martin, M. Hervieu, and B.Raveau, Solid State Commun. 122, 335 (2002).12 R. Mahendiran, A. Maignan, S. Hébert, C. Martin, M. Hervieu, B.Raveau, J. F. Mitchell, and P. Schiffer, Phys. Rev. Lett. 89,286602 (2002).13 V. Hardy, S. Hébert, A. Maignan, C. Martin, M. Hervieu, and B.Raveau, J. Magn. Magn. Mater. 264, 183 (2003).14 L. Ghivelder, R. S. Freitas, M. G. das Virgens, H. Martinho, L.Granja, G. Leyva, P. Levy, and F. Parisi, Phys. Rev. B 69,214414 (2004).15 A. Aliev, S. Abdulvagitov, A. Batdalov, I. Kamilov, O. Gor-benko, and V. Amelichev, Pis’ma Zh. Eksp. Teor. Fiz. 72, 668(2000) [JETP Lett. 72, 464 (2000)].16 N. A. Babushkina, L. M. Belova, V. I. Ozhogin, O. Y. Gorbenko,A. R. Kaul, A. A. Bosak, D. I. Khomskii, and K. I. Kugel, J.Appl. Phys. 83, 7369 (1998).17 C. Martin, A. Maignan, M. Hervieu, and B. Raveau, Phys. Rev. B60, 12 191 (1999).18 N. A. Babushkina, E. A. Chistotina, O. Y. Gorbenko, A. R. Kaul,D. I. Khomskii, and K. I. Kugel, Phys. Rev. B 67, 100410(R)(2003).19 Y. Tomioka, H. Kuwahara, A. Asamitsu, M. Kasai, and Y. Tokura,Appl. Phys. Lett. 70, 3609 (1997).20 E. Vives, J. Ortin, L. Mañosa, I. Ráfols, R. Pérez-Magrané, andA. Planes, Phys. Rev. Lett. 72, 1694 (1994).21 D. Khomskii and L. Khomskii, Phys. Rev. B 67, 052406 (2003).22 K. Binder and A. P. Young, Rev. Mod. Phys. 58, 801 (1986).23 M. E. Zhitomirsky, Phys. Rev. B 67, 104421 (2003).BRIEF REPORTS PHYSICAL REVIEW B 70, 212411 (2004)212411-4

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Quenched-disorder-induced magnetization jumps in
                    
                      
                        
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Magnetic field induced steplike changes in magnetization and resistivity of Sm1-xSrxMnO3 manganites were studied. A strong dependence of these features on the cooling rate was observed. Magnetostriction, however, does not show the presence of large strain in our samples. From all these features we can rule out the conventional explanation of magnetization jumps as a consequence of martensitic transition. We propose instead that quenched by fast cooling disorder leads to the formation of an inhomogeneous metastable state and to subsequent magnetization jumps

NARCIS 

   University of GroningenQuenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3Fisher, LM; Kalinov, AV; Voloshin, IF; Babushkina, NA; Khomskii, DI; Zhang, Y; Palstra, TTMPublished in:Physical Review. B: Condensed Matter and Materials PhysicsDOI:10.1103/PhysRevB.70.212411IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2004Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Fisher, LM., Kalinov, AV., Voloshin, IF., Babushkina, NA., Khomskii, DI., Zhang, Y., & Palstra, TTM. (2004).Quenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3. Physical Review. B: Condensed Matterand Materials Physics, 70(21), [212411]. https://doi.org/10.1103/PhysRevB.70.212411CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 26-04-2023Quenched-disorder-induced magnetization jumps in„Sm,Sr…MnO 3L. M. Fisher,1 A. V. Kalinov,1,2,* I. F. Voloshin,1 N. A. Babushkina,3 D. I. Khomskii,2,4 Y. Zhang,5 and T. T. M. Palstra21All-Russian Electrical Engineering Institute, 12 Krasnokazarmennaya Street, 111250 Moscow, Russia2Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands3Institute of Molecular Physics, Russian Research Center “Kurchatov Institute,” Kurchatov Square 1, 123182 Moscow, Russia4II Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany5Department of Physics, Leiden University, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands(Received 29 July 2004; published 30 December 2004)Magnetic field induced steplike changes in magnetization and resistivity of Sm1−x rxMnO3 manganites werestudied. A strong dependence of these features on the cooling rate was observed. Magnetostriction, however,does not show the presence of large strain in our samples. From all these features we can rule out theconventional explanation of magnetization jumps as a consequence of martensitic transition. We proposeinstead that quenched by fast cooling disorder leads to the formation of an inhomogeneous metastable state andto subsequent magnetization jumps.DOI: 10.1103/PhysRevB.70.212411 PACS number(s): 75.30.Kz, 71.30.1h, 75.47.LxMagnetic field-induced first order phase transitions attracta lot of attention both in conventional antiferromagnets(AFM)1 and in mixed-valence manganites( ee Ref. 2 andreferences therein) as well as in some pseudobinarysystems.3,4 In AFM these transitions are usually reversibleand relatively broad.1 In diluted metamagnets(for example,FexMg1−xCl2) they may be steep(avalanchelike) andhysteretic.5 In manganites such transitions may be sharp orbroad, reversible or strongly hysteretic6 depending on chemi-cal composition and temperature, and are often accompaniedby structural and insulator-to-metal(I-M ) transition.7–9Recently, the field-induced phase transition to a ferromag-netic (FM) state was shown to be discontinuous at lowT,5 K in ceramic Mn-doped Pr0.5Ca0.5MnO3,10,11 in ceramicsand single crystal of Pr1−xCaxMnO3 sx=0.3–0.37d12,13and inGd5sSiGed4 alloys.3,4 The position and number of steps de-pend on the magneto-temperature history and on the mag-netic field sweep rate.3 This was interpreted as the result ofsome kind of martensitic transformation. However, this sce-nario is not clear because grain boundaries in ceramics couldbe intrinsic barriers for domain-wall movement. Ghivelderetal.14 have observed a huge temperature increase at suchabrupt field-induced transition(from 2.5 to 30 K), whereasthe specific heat before and after transition differs only by10%. This implies that a large(magnetic) entropy is frozen inthe sample and abruptly released upon increase of the mag-netic field. The authors of Ref. 14 have proposed a model inwhich the local AFM-FM transition releases the heat locallyand triggers a heat avalanche leading to the observed mag-netization jumps. In this case, the step should have somefinite characteristic time scale of the order of a thermal re-laxation time. However, only the magnetic field width of thestep was discussed and was found to be less than 2 Oe12 oreven strictly zero.14In this paper we show that steplike behavior exists in themagnetizationM and resistivityr but not in the magneto-striction of Sm1−xSrxMn18O3 (x=0.45, 0.5) ceramics. Thesesteps have a characteristic time scale of the order of 1 mswhich does not depend on the magnetic field sweep rate.Moreover, the low-field low-temperature magnetic state itselfstrongly depends on the zero-field cooling rate. There are noM and r steps for slowlys1 K/mind cooled samples, butthey exist only for rapidly cooled samples. In the latter casethere is an additional linear term in the specific heat vs tem-perature dependence. We suggest that frozen magnetic disor-der and corresponding entropy is responsible for the largeoverheating at the avalanchelike transition to the FM stateupon increasing the magnetic field.Ceramic Sm1−xSrxMn18O3 samples withx=0.45, 0.5 andsNdEud0.55Sr0.45Mn18O3 were prepared by a solid-state reac-tion technique, described in Ref. 15. The Nd/Eu ratio wasselected to fit the Sm ionic radius. The magnetic and electricbehavior of SmSr and(NdEu)Sr samples is qualitativelyidentical [see Fig. 3(b)]. The enrichment of the samples by18O was performed atT=950 °C and at a pressurep=1 barfor 200 h using the method reported in Ref. 16. Magnetiza-tion was measured by a Quantum Design MPMS-7 SQUIDmagnetometer and by a vibrating sample magnetometer.High-speed(up to 100 000 samplings per second) measure-ments of the magnetization were performed using Fitz’stechnique and a fast analog-to-digital data acquisition board(Data Translation). Resistivity, specific heat, and magneto-striction were measured in PPMS-9 cryostat. To measuremagnetostriction we used WK-06-062AP-350 strain gauges(Vishay Intertechnology) bonded to the sample with a properepoxy. The striction was detected by the change in resistanceof the strain gauge.Sm1−xSrxMnO3 with x<0.5 is known to be in the vicinityof the I-M and AFM-FM transition.17 So, for this system theelectronic and magnetic state can be tuned by the applicationof a magnetic field or by oxygen-isotope substitution.Sm0.5Sr0.5Mn18O3 is an insulator in the low-temperatureground state, and undergoes an I-M transition after18O-to-16O substitution, after reduction of the doping level tox=0.45, or under application of the magnetic field of the orderof 1 T.18 Our magnetization data(Fig. 1) show that there arePHYSICAL REVIEW B 70, 212411(2004)1098-0121/2004/70(21)/212411(4)/$22.50 ©2004 The American Physical Society212411-1two types of field-induced transition for18O samples: at lowtemperatures there appears an irreversible transition from anAFM to FM state, and at high temperaturesT.Tc—a revers-ible albeit slightly hysteretic PM-FM transition. Magneto-striction of about 2310−4 is clearly seen to accompany thePM-FM transition(upper inset) in accordance with the dataof Ref. 19. The 1/x data just aboveTc show a tendency forAFM interactions that competes with FM ordering at inter-mediate temperatures.The irreversible metamagnetic AFM-FM transition isshown to be steplike(Fig. 2) after zero-field cooling. Wehave observed that the step location depends on the sweeprate of the following magnetic field: the smaller the sweeprate, the larger the field value needed to realize the transition.For the Sm0.5Sr0.5Mn18O3 sample at the rateø250 Oe/s thetransition becomes smooth. This shows that the steplike tran-sition is not an intrinsic property of a compound. Two ques-tions arise at this point:(i) how sharp are these steps and(ii )is M a function of the magnetic field along all the steps or isonly the start of the transition triggered by the magneticfield?To resolve these problems we have studied theMsHdsteps at different sweep rates with our high-speed experimen-tal setup with 10ms resolution. The results shown in theinset to Fig. 2 demonstrate the finite width of the transitionof the order of 1 ms. Note that this curve is the same fordifferent sweep rates200–3000 Oe/sd. Being triggered, thetransition will complete in a definite time independent on thefurther changes of theH. In the case of Sm0.5Sr0.5Mn18O3,this time scale is approximately 10 times higher(not shown).Thus, our samples with a relatively small difference in Srcontent exhibit a factor of 10 difference in the transitiontime. This fact cannot be easily reconciled with the scenarioof a martensitic transition because the microstructure of bothsamples is identical. Moreover, a distribution of avalanchesin martensitic transformations has usually no characteristictime scales20 unlike our observations.To further elucidate the origin of such sharp transitions,we have checked the effects of the cooling rate on the low-temperature magnetic state(Fig. 3). The quenched-in disor-der should be strongly affected by the cooling rate. In thecase of martensitic transformation,20 a slow cooling rateleads to a low defect concentration so that the strains arereleased via large avalanches. On the other hand, fast coolingresults in a large number of defects and thus leads to a se-quence of many small avalanches. However, as we will dis-cuss below, the behavior observed in our experiments withdifferent cooling rates shows the opposite tendency. This isin our opinion a strong argument against the interpretation ofthe jumps as a consequence of martensitic phenomena.Two cooling rates were used in our experiments. In thefirst, slow cooling, the sample was cooled at the rate of1 K/min from 300 K to 5 K in zero applied field for trans-port and specific heat measurements and 100 Oe for magne-tization experiments. In the second, fast cooling regime, thecooling rate was 10 K/min for resistivity and specific heatmeasurements and approximately 20 K/min for magnetiza-tion. Usually, no specific information is provided in the lit-erature on the employed cooling rate in manganite research,and we assume that most results are obtained using a rela-tively fast cooling rate.Two key points should be noted in the data of Fig. 3. Thefirst is a huge thermal hysteresis for the data obtained onheating and cooling, which is generally considered to be afingerprint of a first order phase transition. The second is astriking difference in the low-temperature states of theFIG. 1. Magnetization loops for Sm0.55Sr0.45MnO3 recorded af-ter zero-field cooling from room temperature. The data for the firstincrease of the magnetic field are shown in the first quadrant andmarked with bold arrows if different from stable curves(III quad-rant). T=5 K (h), 55 K (s), 120 K (n), and 140 K(,). The upperleft inset shows magnetostriction at 120 K, the lower right one pre-sents a high-temperature tail of inverse susceptibility atm0H=0.1 T.FIG. 2. The dependence of the magnetization jump on the mag-netic field sweep rate for Sm0.55Sr0.45Mn18O3 (a) andSm0.5Sr0.5Mn18O3 (b) at T=5 K. Inset shows the time dependenceof the magnetization during the jump. This dependence is the samefor the sweep rates in the range 200–3000 Oe/s.BRIEF REPORTS PHYSICAL REVIEW B70, 212411(2004)212411-2fast- and slow-cooled samples. For the former, we observe alow-magnetization state with a relatively high resistivity. Forthe latter, the magnetization is 10 times higher and the resis-tivity is smaller. The additional linear term in the specificheat appears for the fast cooled sample as shown in the insetto Fig. 3(a). These differences diminish upon heating anddisappears atT<45 K.The low-temperature magnetization and resistivity loopsafter slow and fast cooling(Fig. 4) have qualitatively differ-ent behavior. The steplike transition inMsHd andrsHd existsonly for fast cooled samples, whereas this transformation issmooth in slow cooled samples. Comparison of the data ofFigs. 4(a) and 4(b) shows that the fast-cooled samples havesignificantly larger resistivity even at the same value ofM[compare, for instance,rsH=0.5,1.1 Td]. This is an evidencefor a quenched disorder in fast-cooled samples(cf. Ref. 21).The other evidence of an additional disorder is shown in theinset to Fig. 3(a). The fitting of the temperature dependenceof the specific heat is the same for both cooling rates exceptan additional linear term of the order of 20% in the fast-cooled sample.(Note, that conductivity in this case is evenlower and the electron term could not be the origin of thischange.) Corresponding extra entropyDS=0.25J/K/mol isof the same order as the entropy change upon PM-FM tran-sition s,0.6 J/K/mold, thus we believe this extra linear termto have essentially magnetic origin, possibly spin-glass-liketype.22 However, there is almost no additional strain(lessthan 10−5) in the fast-cooled sample and the magnetostrictionis smooth for both histories. This, together with the oppositedependence of the behavior of our samples on the coolingrate, mentioned above, in our opinion rules out the descrip-tion of these phenomena as a consequence of a martensiticnature of the transition.Upon cooling, the AFM-FM competition may result in astrongly disordered magnetic state, which has an excess spe-cific heat and enhanced magnetocaloric effect.23 Ferromag-netic ordering with the external magnetic field would lead tothe reduction of this extra entropy. In this case, the localrelease of the frozen entropy may result in the avalanchelikeoverheating of the sample because the higher the temperaturethe more tendency to ferromagnetism is observed at low tem-peratures(cf. the data for 5 and 55 K in Fig. 1). So, both themagnetization and resistivity change in a jumplike fashion.Such effect was observed recently14 on the steplike transi-tion. This scenario assumes the time scale of the transition tobe inversely proportional to the thermal conductivity of thesample. This is exactly the case if one comparesSm1−xSrxMn18O3 with x=0.45 and 0.5. The resistivity ofSm0.5Sr0.5Mn18O3 is at least four orders of magnitudehigher18 so that the thermal conductivity should be lower. Werecall that the observed time scale of the jump forSm0.5Sr0.5Mn18O3 is 10 times larger than forSm0.55Sr0.45Mn18O3.Summarizing, we studied the magnetization and resistiv-ity jumps in Sm1−xSrxMn18O3, especially their dependenceon the cooling rate. The slows1 K/mind cooled samplesdemonstrate a smooth AFM-FM transition upon increase ofthe magnetic field, in contrast to the fast,10 K/mindcooled samples where this transition is steplike with a char-acteristic time scale of 1 ms. The results obtained(theFIG. 3. The temperature dependences of the low-fields0.01 Tdmagnetization (a) and zero-field resistivity (b) ofSm0.55Sr0.45Mn18O3 obtained for different temperature histories:(s) slow cooling,(P) heating after slow cooling, and(n) heatingafter fast cooling. Insets show the temperature dependence of thespecific heat(a) and resistivity(b) of sNdEud0.55Sr0.45Mn18O3 forthe same temperature histories.FIG. 4. Magnetization (a) and resistivity (b) loops forSm0.55Sr0.45Mn18O3 recorded at 5 K after slow and fast cooling inzero field, which demonstrate the absence of jumps for slowlycooled samples. The inset shows a minor effect of the cooling rateon the magnetostriction. Here the parabolic increase is caused bythe magnetoresistance of the gauge itself.BRIEF REPORTS PHYSICAL REVIEW B70, 212411(2004)212411-3dependence of the jumps on the cooling rate; the constanttime scale of the jumps, independent on the field-sweep rate;the behavior of specific heat; the absence of noticeable mag-netostriction) disagree with the often used interpretation thatthe magnetization steps originate from the strain release at amartensitic transition. We suggest that the frozen disorderand the associated entropy is the origin of an excess specificheat which is released in an avalanchelike way upon apply-ing a magnetic field, resulting in a heat burst in the sampleand in steps in the magnetization and resistivity.This study was supported by the Netherlands Organiza-tion for the Advancement of Pure Research(NWO) and IN-TAS project(01-2008).*Corresponding author. Email address: kalinov@vei.ru1E. Stryjewski and N. Giordano, Adv. Phys.26, 487 (1977).2J. M. D. Coey, M. Viret, and S. von Molnár, Adv. Phys.48, 167(1999).3V. Hardy et al., Phys. Rev. B69, 020407(R) (2004).4E. M. Levin, K. A. Gschneidner, Jr., and V. K. Pecharsky, Phys.Rev. B 65, 214427(2002).5J. Kushauer, R. van Bentum, W. Kleemann, and D. Bertrand,Phys. Rev. B53, 11 647(1996).6G. Xiao, G. Q. Gong, C. L. Canedy, E. J. McNiff, Jr., and A.Gupta, J. Appl. Phys.81, 5324(1997).7Y. Tomioka, A. Asamitsu, Y. Moritomo, H. Kuwahara, and Y.Tokura, Phys. Rev. Lett.74, 5108(1995).8Y. Tomioka, A. Asamitsu, H. Kuwahara, Y. Moritomo, and Y.Tokura, Phys. Rev. B53, R1 689(1996).9H. Yoshizawa, H. Kawano, Y. Tomioka, and Y. Tokura, Phys.Rev. B 52, R13 145(1995).10S. Hébert, A. Maignan, V. Hardy, C. Martin, M. Hervieu, B.Raveau, R. Mahendiran, and P. Schiffer, Eur. Phys. J. B29, 419(2002).11S. Hébert, A. Maignan, V. Hardy, C. Martin, M. Hervieu, and B.Raveau, Solid State Commun.122, 335 (2002).12R. Mahendiran, A. Maignan, S. Hébert, C. Martin, M. Hervieu, B.Raveau, J. F. Mitchell, and P. Schiffer, Phys. Rev. Lett.89,286602(2002).13V. Hardy, S. Hébert, A. Maignan, C. Martin, M. Hervieu, and B.Raveau, J. Magn. Magn. Mater.264, 183 (2003).14L. Ghivelder, R. S. Freitas, M. G. das Virgens, H. Martinho, L.Granja, G. Leyva, P. Levy, and F. Parisi, Phys. Rev. B69,214414(2004).15A. Aliev, S. Abdulvagitov, A. Batdalov, I. Kamilov, O. Gor-benko, and V. Amelichev, Pis’ma Zh. Eksp. Teor. Fiz.72, 668(2000) [JETP Lett. 72, 464 (2000)].16N. A. Babushkina, L. M. Belova, V. I. Ozhogin, O. Y. Gorbenko,A. R. Kaul, A. A. Bosak, D. I. Khomskii, and K. I. Kugel, J.Appl. Phys. 83, 7369(1998).17C. Martin, A. Maignan, M. Hervieu, and B. Raveau, Phys. Rev. B60, 12 191(1999).18N. A. Babushkina, E. A. Chistotina, O. Y. Gorbenko, A. R. Kaul,D. I. Khomskii, and K. I. Kugel, Phys. Rev. B67, 100410(R)(2003).19Y. Tomioka, H. Kuwahara, A. Asamitsu, M. Kasai, and Y. Tokura,Appl. Phys. Lett.70, 3609(1997).20E. Vives, J. Ortin, L. Mañosa, I. Ráfols, R. Pérez-Magrané, andA. Planes, Phys. Rev. Lett.72, 1694(1994).21D. Khomskii and L. Khomskii, Phys. Rev. B67, 052406(2003).22K. Binder and A. P. Young, Rev. Mod. Phys.58, 801 (1986).23M. E. Zhitomirsky, Phys. Rev. B67, 104421(2003).BRIEF REPORTS PHYSICAL REVIEW B70, 212411(2004)212411-4

Magnetic field induced steplike changes in magnetization and resistivity of Sm1-xSrxMnO3 manganites were studied. A strong dependence of these features on the cooling rate was observed. Magnetostriction, however, does not show the presence of large strain in our samples. From all these features we can rule out the conventional explanation of magnetization jumps as a consequence of martensitic transition. We propose instead that quenched by fast cooling disorder leads to the formation of an inhomogeneous metastable state and to subsequent magnetization jumps.</p

ARTS repository - University of Groningen

   University of GroningenQuenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3Fisher, LM; Kalinov, AV; Voloshin, IF; Babushkina, NA; Khomskii, DI; Zhang, Y; Palstra, TTMPublished in:Physical Review. B: Condensed Matter and Materials PhysicsDOI:10.1103/PhysRevB.70.212411IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2004Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Fisher, LM., Kalinov, AV., Voloshin, IF., Babushkina, NA., Khomskii, DI., Zhang, Y., & Palstra, TTM. (2004).Quenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3. Physical Review. B: Condensed Matterand Materials Physics, 70(21), [212411]. https://doi.org/10.1103/PhysRevB.70.212411CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 13-02-2023Quenched-disorder-induced magnetization jumps in„Sm,Sr…MnO 3L. M. Fisher,1 A. V. Kalinov,1,2,* I. F. Voloshin,1 N. A. Babushkina,3 D. I. Khomskii,2,4 Y. Zhang,5 and T. T. M. Palstra21All-Russian Electrical Engineering Institute, 12 Krasnokazarmennaya Street, 111250 Moscow, Russia2Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands3Institute of Molecular Physics, Russian Research Center “Kurchatov Institute,” Kurchatov Square 1, 123182 Moscow, Russia4II Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany5Department of Physics, Leiden University, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands(Received 29 July 2004; published 30 December 2004)Magnetic field induced steplike changes in magnetization and resistivity of Sm1−x rxMnO3 manganites werestudied. A strong dependence of these features on the cooling rate was observed. Magnetostriction, however,does not show the presence of large strain in our samples. From all these features we can rule out theconventional explanation of magnetization jumps as a consequence of martensitic transition. We proposeinstead that quenched by fast cooling disorder leads to the formation of an inhomogeneous metastable state andto subsequent magnetization jumps.DOI: 10.1103/PhysRevB.70.212411 PACS number(s): 75.30.Kz, 71.30.1h, 75.47.LxMagnetic field-induced first order phase transitions attracta lot of attention both in conventional antiferromagnets(AFM)1 and in mixed-valence manganites( ee Ref. 2 andreferences therein) as well as in some pseudobinarysystems.3,4 In AFM these transitions are usually reversibleand relatively broad.1 In diluted metamagnets(for example,FexMg1−xCl2) they may be steep(avalanchelike) andhysteretic.5 In manganites such transitions may be sharp orbroad, reversible or strongly hysteretic6 depending on chemi-cal composition and temperature, and are often accompaniedby structural and insulator-to-metal(I-M ) transition.7–9Recently, the field-induced phase transition to a ferromag-netic (FM) state was shown to be discontinuous at lowT,5 K in ceramic Mn-doped Pr0.5Ca0.5MnO3,10,11 in ceramicsand single crystal of Pr1−xCaxMnO3 sx=0.3–0.37d12,13and inGd5sSiGed4 alloys.3,4 The position and number of steps de-pend on the magneto-temperature history and on the mag-netic field sweep rate.3 This was interpreted as the result ofsome kind of martensitic transformation. However, this sce-nario is not clear because grain boundaries in ceramics couldbe intrinsic barriers for domain-wall movement. Ghivelderetal.14 have observed a huge temperature increase at suchabrupt field-induced transition(from 2.5 to 30 K), whereasthe specific heat before and after transition differs only by10%. This implies that a large(magnetic) entropy is frozen inthe sample and abruptly released upon increase of the mag-netic field. The authors of Ref. 14 have proposed a model inwhich the local AFM-FM transition releases the heat locallyand triggers a heat avalanche leading to the observed mag-netization jumps. In this case, the step should have somefinite characteristic time scale of the order of a thermal re-laxation time. However, only the magnetic field width of thestep was discussed and was found to be less than 2 Oe12 oreven strictly zero.14In this paper we show that steplike behavior exists in themagnetizationM and resistivityr but not in the magneto-striction of Sm1−xSrxMn18O3 (x=0.45, 0.5) ceramics. Thesesteps have a characteristic time scale of the order of 1 mswhich does not depend on the magnetic field sweep rate.Moreover, the low-field low-temperature magnetic state itselfstrongly depends on the zero-field cooling rate. There are noM and r steps for slowlys1 K/mind cooled samples, butthey exist only for rapidly cooled samples. In the latter casethere is an additional linear term in the specific heat vs tem-perature dependence. We suggest that frozen magnetic disor-der and corresponding entropy is responsible for the largeoverheating at the avalanchelike transition to the FM stateupon increasing the magnetic field.Ceramic Sm1−xSrxMn18O3 samples withx=0.45, 0.5 andsNdEud0.55Sr0.45Mn18O3 were prepared by a solid-state reac-tion technique, described in Ref. 15. The Nd/Eu ratio wasselected to fit the Sm ionic radius. The magnetic and electricbehavior of SmSr and(NdEu)Sr samples is qualitativelyidentical [see Fig. 3(b)]. The enrichment of the samples by18O was performed atT=950 °C and at a pressurep=1 barfor 200 h using the method reported in Ref. 16. Magnetiza-tion was measured by a Quantum Design MPMS-7 SQUIDmagnetometer and by a vibrating sample magnetometer.High-speed(up to 100 000 samplings per second) measure-ments of the magnetization were performed using Fitz’stechnique and a fast analog-to-digital data acquisition board(Data Translation). Resistivity, specific heat, and magneto-striction were measured in PPMS-9 cryostat. To measuremagnetostriction we used WK-06-062AP-350 strain gauges(Vishay Intertechnology) bonded to the sample with a properepoxy. The striction was detected by the change in resistanceof the strain gauge.Sm1−xSrxMnO3 with x<0.5 is known to be in the vicinityof the I-M and AFM-FM transition.17 So, for this system theelectronic and magnetic state can be tuned by the applicationof a magnetic field or by oxygen-isotope substitution.Sm0.5Sr0.5Mn18O3 is an insulator in the low-temperatureground state, and undergoes an I-M transition after18O-to-16O substitution, after reduction of the doping level tox=0.45, or under application of the magnetic field of the orderof 1 T.18 Our magnetization data(Fig. 1) show that there arePHYSICAL REVIEW B 70, 212411(2004)1098-0121/2004/70(21)/212411(4)/$22.50 ©2004 The American Physical Society212411-1two types of field-induced transition for18O samples: at lowtemperatures there appears an irreversible transition from anAFM to FM state, and at high temperaturesT.Tc—a revers-ible albeit slightly hysteretic PM-FM transition. Magneto-striction of about 2310−4 is clearly seen to accompany thePM-FM transition(upper inset) in accordance with the dataof Ref. 19. The 1/x data just aboveTc show a tendency forAFM interactions that competes with FM ordering at inter-mediate temperatures.The irreversible metamagnetic AFM-FM transition isshown to be steplike(Fig. 2) after zero-field cooling. Wehave observed that the step location depends on the sweeprate of the following magnetic field: the smaller the sweeprate, the larger the field value needed to realize the transition.For the Sm0.5Sr0.5Mn18O3 sample at the rateø250 Oe/s thetransition becomes smooth. This shows that the steplike tran-sition is not an intrinsic property of a compound. Two ques-tions arise at this point:(i) how sharp are these steps and(ii )is M a function of the magnetic field along all the steps or isonly the start of the transition triggered by the magneticfield?To resolve these problems we have studied theMsHdsteps at different sweep rates with our high-speed experimen-tal setup with 10ms resolution. The results shown in theinset to Fig. 2 demonstrate the finite width of the transitionof the order of 1 ms. Note that this curve is the same fordifferent sweep rates200–3000 Oe/sd. Being triggered, thetransition will complete in a definite time independent on thefurther changes of theH. In the case of Sm0.5Sr0.5Mn18O3,this time scale is approximately 10 times higher(not shown).Thus, our samples with a relatively small difference in Srcontent exhibit a factor of 10 difference in the transitiontime. This fact cannot be easily reconciled with the scenarioof a martensitic transition because the microstructure of bothsamples is identical. Moreover, a distribution of avalanchesin martensitic transformations has usually no characteristictime scales20 unlike our observations.To further elucidate the origin of such sharp transitions,we have checked the effects of the cooling rate on the low-temperature magnetic state(Fig. 3). The quenched-in disor-der should be strongly affected by the cooling rate. In thecase of martensitic transformation,20 a slow cooling rateleads to a low defect concentration so that the strains arereleased via large avalanches. On the other hand, fast coolingresults in a large number of defects and thus leads to a se-quence of many small avalanches. However, as we will dis-cuss below, the behavior observed in our experiments withdifferent cooling rates shows the opposite tendency. This isin our opinion a strong argument against the interpretation ofthe jumps as a consequence of martensitic phenomena.Two cooling rates were used in our experiments. In thefirst, slow cooling, the sample was cooled at the rate of1 K/min from 300 K to 5 K in zero applied field for trans-port and specific heat measurements and 100 Oe for magne-tization experiments. In the second, fast cooling regime, thecooling rate was 10 K/min for resistivity and specific heatmeasurements and approximately 20 K/min for magnetiza-tion. Usually, no specific information is provided in the lit-erature on the employed cooling rate in manganite research,and we assume that most results are obtained using a rela-tively fast cooling rate.Two key points should be noted in the data of Fig. 3. Thefirst is a huge thermal hysteresis for the data obtained onheating and cooling, which is generally considered to be afingerprint of a first order phase transition. The second is astriking difference in the low-temperature states of theFIG. 1. Magnetization loops for Sm0.55Sr0.45MnO3 recorded af-ter zero-field cooling from room temperature. The data for the firstincrease of the magnetic field are shown in the first quadrant andmarked with bold arrows if different from stable curves(III quad-rant). T=5 K (h), 55 K (s), 120 K (n), and 140 K(,). The upperleft inset shows magnetostriction at 120 K, the lower right one pre-sents a high-temperature tail of inverse susceptibility atm0H=0.1 T.FIG. 2. The dependence of the magnetization jump on the mag-netic field sweep rate for Sm0.55Sr0.45Mn18O3 (a) andSm0.5Sr0.5Mn18O3 (b) at T=5 K. Inset shows the time dependenceof the magnetization during the jump. This dependence is the samefor the sweep rates in the range 200–3000 Oe/s.BRIEF REPORTS PHYSICAL REVIEW B70, 212411(2004)212411-2fast- and slow-cooled samples. For the former, we observe alow-magnetization state with a relatively high resistivity. Forthe latter, the magnetization is 10 times higher and the resis-tivity is smaller. The additional linear term in the specificheat appears for the fast cooled sample as shown in the insetto Fig. 3(a). These differences diminish upon heating anddisappears atT<45 K.The low-temperature magnetization and resistivity loopsafter slow and fast cooling(Fig. 4) have qualitatively differ-ent behavior. The steplike transition inMsHd andrsHd existsonly for fast cooled samples, whereas this transformation issmooth in slow cooled samples. Comparison of the data ofFigs. 4(a) and 4(b) shows that the fast-cooled samples havesignificantly larger resistivity even at the same value ofM[compare, for instance,rsH=0.5,1.1 Td]. This is an evidencefor a quenched disorder in fast-cooled samples(cf. Ref. 21).The other evidence of an additional disorder is shown in theinset to Fig. 3(a). The fitting of the temperature dependenceof the specific heat is the same for both cooling rates exceptan additional linear term of the order of 20% in the fast-cooled sample.(Note, that conductivity in this case is evenlower and the electron term could not be the origin of thischange.) Corresponding extra entropyDS=0.25J/K/mol isof the same order as the entropy change upon PM-FM tran-sition s,0.6 J/K/mold, thus we believe this extra linear termto have essentially magnetic origin, possibly spin-glass-liketype.22 However, there is almost no additional strain(lessthan 10−5) in the fast-cooled sample and the magnetostrictionis smooth for both histories. This, together with the oppositedependence of the behavior of our samples on the coolingrate, mentioned above, in our opinion rules out the descrip-tion of these phenomena as a consequence of a martensiticnature of the transition.Upon cooling, the AFM-FM competition may result in astrongly disordered magnetic state, which has an excess spe-cific heat and enhanced magnetocaloric effect.23 Ferromag-netic ordering with the external magnetic field would lead tothe reduction of this extra entropy. In this case, the localrelease of the frozen entropy may result in the avalanchelikeoverheating of the sample because the higher the temperaturethe more tendency to ferromagnetism is observed at low tem-peratures(cf. the data for 5 and 55 K in Fig. 1). So, both themagnetization and resistivity change in a jumplike fashion.Such effect was observed recently14 on the steplike transi-tion. This scenario assumes the time scale of the transition tobe inversely proportional to the thermal conductivity of thesample. This is exactly the case if one comparesSm1−xSrxMn18O3 with x=0.45 and 0.5. The resistivity ofSm0.5Sr0.5Mn18O3 is at least four orders of magnitudehigher18 so that the thermal conductivity should be lower. Werecall that the observed time scale of the jump forSm0.5Sr0.5Mn18O3 is 10 times larger than forSm0.55Sr0.45Mn18O3.Summarizing, we studied the magnetization and resistiv-ity jumps in Sm1−xSrxMn18O3, especially their dependenceon the cooling rate. The slows1 K/mind cooled samplesdemonstrate a smooth AFM-FM transition upon increase ofthe magnetic field, in contrast to the fast,10 K/mindcooled samples where this transition is steplike with a char-acteristic time scale of 1 ms. The results obtained(theFIG. 3. The temperature dependences of the low-fields0.01 Tdmagnetization (a) and zero-field resistivity (b) ofSm0.55Sr0.45Mn18O3 obtained for different temperature histories:(s) slow cooling,(P) heating after slow cooling, and(n) heatingafter fast cooling. Insets show the temperature dependence of thespecific heat(a) and resistivity(b) of sNdEud0.55Sr0.45Mn18O3 forthe same temperature histories.FIG. 4. Magnetization (a) and resistivity (b) loops forSm0.55Sr0.45Mn18O3 recorded at 5 K after slow and fast cooling inzero field, which demonstrate the absence of jumps for slowlycooled samples. The inset shows a minor effect of the cooling rateon the magnetostriction. Here the parabolic increase is caused bythe magnetoresistance of the gauge itself.BRIEF REPORTS PHYSICAL REVIEW B70, 212411(2004)212411-3dependence of the jumps on the cooling rate; the constanttime scale of the jumps, independent on the field-sweep rate;the behavior of specific heat; the absence of noticeable mag-netostriction) disagree with the often used interpretation thatthe magnetization steps originate from the strain release at amartensitic transition. We suggest that the frozen disorderand the associated entropy is the origin of an excess specificheat which is released in an avalanchelike way upon apply-ing a magnetic field, resulting in a heat burst in the sampleand in steps in the magnetization and resistivity.This study was supported by the Netherlands Organiza-tion for the Advancement of Pure Research(NWO) and IN-TAS project(01-2008).*Corresponding author. Email address: kalinov@vei.ru1E. Stryjewski and N. Giordano, Adv. Phys.26, 487 (1977).2J. M. D. Coey, M. Viret, and S. von Molnár, Adv. Phys.48, 167(1999).3V. Hardy et al., Phys. Rev. B69, 020407(R) (2004).4E. M. Levin, K. A. Gschneidner, Jr., and V. K. Pecharsky, Phys.Rev. B 65, 214427(2002).5J. Kushauer, R. van Bentum, W. Kleemann, and D. Bertrand,Phys. Rev. B53, 11 647(1996).6G. Xiao, G. Q. Gong, C. L. Canedy, E. J. McNiff, Jr., and A.Gupta, J. Appl. Phys.81, 5324(1997).7Y. Tomioka, A. Asamitsu, Y. Moritomo, H. Kuwahara, and Y.Tokura, Phys. Rev. Lett.74, 5108(1995).8Y. Tomioka, A. Asamitsu, H. Kuwahara, Y. Moritomo, and Y.Tokura, Phys. Rev. B53, R1 689(1996).9H. Yoshizawa, H. Kawano, Y. Tomioka, and Y. Tokura, Phys.Rev. B 52, R13 145(1995).10S. Hébert, A. Maignan, V. Hardy, C. Martin, M. Hervieu, B.Raveau, R. Mahendiran, and P. Schiffer, Eur. Phys. J. B29, 419(2002).11S. Hébert, A. Maignan, V. Hardy, C. Martin, M. Hervieu, and B.Raveau, Solid State Commun.122, 335 (2002).12R. Mahendiran, A. Maignan, S. Hébert, C. Martin, M. Hervieu, B.Raveau, J. F. Mitchell, and P. Schiffer, Phys. Rev. Lett.89,286602(2002).13V. Hardy, S. Hébert, A. Maignan, C. Martin, M. Hervieu, and B.Raveau, J. Magn. Magn. Mater.264, 183 (2003).14L. Ghivelder, R. S. Freitas, M. G. das Virgens, H. Martinho, L.Granja, G. Leyva, P. Levy, and F. Parisi, Phys. Rev. B69,214414(2004).15A. Aliev, S. Abdulvagitov, A. Batdalov, I. Kamilov, O. Gor-benko, and V. Amelichev, Pis’ma Zh. Eksp. Teor. Fiz.72, 668(2000) [JETP Lett. 72, 464 (2000)].16N. A. Babushkina, L. M. Belova, V. I. Ozhogin, O. Y. Gorbenko,A. R. Kaul, A. A. Bosak, D. I. Khomskii, and K. I. Kugel, J.Appl. Phys. 83, 7369(1998).17C. Martin, A. Maignan, M. Hervieu, and B. Raveau, Phys. Rev. B60, 12 191(1999).18N. A. Babushkina, E. A. Chistotina, O. Y. Gorbenko, A. R. Kaul,D. I. Khomskii, and K. I. Kugel, Phys. Rev. B67, 100410(R)(2003).19Y. Tomioka, H. Kuwahara, A. Asamitsu, M. Kasai, and Y. Tokura,Appl. Phys. Lett.70, 3609(1997).20E. Vives, J. Ortin, L. Mañosa, I. Ráfols, R. Pérez-Magrané, andA. Planes, Phys. Rev. Lett.72, 1694(1994).21D. Khomskii and L. Khomskii, Phys. Rev. B67, 052406(2003).22K. Binder and A. P. Young, Rev. Mod. Phys.58, 801 (1986).23M. E. Zhitomirsky, Phys. Rev. B67, 104421(2003).BRIEF REPORTS PHYSICAL REVIEW B70, 212411(2004)212411-4

Quenched-disorder-induced magnetization jumps in(Sm,Sr)MnO3

   University of GroningenQuenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3Fisher, LM; Kalinov, AV; Voloshin, IF; Babushkina, NA; Khomskii, DI; Zhang, Y; Palstra, TTMPublished in:Physical Review. B: Condensed Matter and Materials PhysicsDOI:10.1103/PhysRevB.70.212411IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2004Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Fisher, LM., Kalinov, AV., Voloshin, IF., Babushkina, NA., Khomskii, DI., Zhang, Y., & Palstra, TTM. (2004).Quenched-disorder-induced magnetization jumps in (Sm,Sr)MnO3. Physical Review. B: Condensed Matterand Materials Physics, 70(21), Article 212411. https://doi.org/10.1103/PhysRevB.70.212411CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 09-09-2023Quenched-disorder-induced magnetization jumps in„Sm,Sr…MnO 3L. M. Fisher,1 A. V. Kalinov,1,2,* I. F. Voloshin,1 N. A. Babushkina,3 D. I. Khomskii,2,4 Y. Zhang,5 and T. T. M. Palstra21All-Russian Electrical Engineering Institute, 12 Krasnokazarmennaya Street, 111250 Moscow, Russia2Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands3Institute of Molecular Physics, Russian Research Center “Kurchatov Institute,” Kurchatov Square 1, 123182 Moscow, Russia4II Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany5Department of Physics, Leiden University, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands(Received 29 July 2004; published 30 December 2004)Magnetic field induced steplike changes in magnetization and resistivity of Sm1−x rxMnO3 manganites werestudied. A strong dependence of these features on the cooling rate was observed. Magnetostriction, however,does not show the presence of large strain in our samples. From all these features we can rule out theconventional explanation of magnetization jumps as a consequence of martensitic transition. We proposeinstead that quenched by fast cooling disorder leads to the formation of an inhomogeneous metastable state andto subsequent magnetization jumps.DOI: 10.1103/PhysRevB.70.212411 PACS number(s): 75.30.Kz, 71.30.1h, 75.47.LxMagnetic field-induced first order phase transitions attracta lot of attention both in conventional antiferromagnets(AFM)1 and in mixed-valence manganites( ee Ref. 2 andreferences therein) as well as in some pseudobinarysystems.3,4 In AFM these transitions are usually reversibleand relatively broad.1 In diluted metamagnets(for example,FexMg1−xCl2) they may be steep(avalanchelike) andhysteretic.5 In manganites such transitions may be sharp orbroad, reversible or strongly hysteretic6 depending on chemi-cal composition and temperature, and are often accompaniedby structural and insulator-to-metal(I-M ) transition.7–9Recently, the field-induced phase transition to a ferromag-netic (FM) state was shown to be discontinuous at lowT,5 K in ceramic Mn-doped Pr0.5Ca0.5MnO3,10,11 in ceramicsand single crystal of Pr1−xCaxMnO3 sx=0.3–0.37d12,13and inGd5sSiGed4 alloys.3,4 The position and number of steps de-pend on the magneto-temperature history and on the mag-netic field sweep rate.3 This was interpreted as the result ofsome kind of martensitic transformation. However, this sce-nario is not clear because grain boundaries in ceramics couldbe intrinsic barriers for domain-wall movement. Ghivelderetal.14 have observed a huge temperature increase at suchabrupt field-induced transition(from 2.5 to 30 K), whereasthe specific heat before and after transition differs only by10%. This implies that a large(magnetic) entropy is frozen inthe sample and abruptly released upon increase of the mag-netic field. The authors of Ref. 14 have proposed a model inwhich the local AFM-FM transition releases the heat locallyand triggers a heat avalanche leading to the observed mag-netization jumps. In this case, the step should have somefinite characteristic time scale of the order of a thermal re-laxation time. However, only the magnetic field width of thestep was discussed and was found to be less than 2 Oe12 oreven strictly zero.14In this paper we show that steplike behavior exists in themagnetizationM and resistivityr but not in the magneto-striction of Sm1−xSrxMn18O3 (x=0.45, 0.5) ceramics. Thesesteps have a characteristic time scale of the order of 1 mswhich does not depend on the magnetic field sweep rate.Moreover, the low-field low-temperature magnetic state itselfstrongly depends on the zero-field cooling rate. There are noM and r steps for slowlys1 K/mind cooled samples, butthey exist only for rapidly cooled samples. In the latter casethere is an additional linear term in the specific heat vs tem-perature dependence. We suggest that frozen magnetic disor-der and corresponding entropy is responsible for the largeoverheating at the avalanchelike transition to the FM stateupon increasing the magnetic field.Ceramic Sm1−xSrxMn18O3 samples withx=0.45, 0.5 andsNdEud0.55Sr0.45Mn18O3 were prepared by a solid-state reac-tion technique, described in Ref. 15. The Nd/Eu ratio wasselected to fit the Sm ionic radius. The magnetic and electricbehavior of SmSr and(NdEu)Sr samples is qualitativelyidentical [see Fig. 3(b)]. The enrichment of the samples by18O was performed atT=950 °C and at a pressurep=1 barfor 200 h using the method reported in Ref. 16. Magnetiza-tion was measured by a Quantum Design MPMS-7 SQUIDmagnetometer and by a vibrating sample magnetometer.High-speed(up to 100 000 samplings per second) measure-ments of the magnetization were performed using Fitz’stechnique and a fast analog-to-digital data acquisition board(Data Translation). Resistivity, specific heat, and magneto-striction were measured in PPMS-9 cryostat. To measuremagnetostriction we used WK-06-062AP-350 strain gauges(Vishay Intertechnology) bonded to the sample with a properepoxy. The striction was detected by the change in resistanceof the strain gauge.Sm1−xSrxMnO3 with x<0.5 is known to be in the vicinityof the I-M and AFM-FM transition.17 So, for this system theelectronic and magnetic state can be tuned by the applicationof a magnetic field or by oxygen-isotope substitution.Sm0.5Sr0.5Mn18O3 is an insulator in the low-temperatureground state, and undergoes an I-M transition after18O-to-16O substitution, after reduction of the doping level tox=0.45, or under application of the magnetic field of the orderof 1 T.18 Our magnetization data(Fig. 1) show that there arePHYSICAL REVIEW B 70, 212411(2004)1098-0121/2004/70(21)/212411(4)/$22.50 ©2004 The American Physical Society212411-1two types of field-induced transition for18O samples: at lowtemperatures there appears an irreversible transition from anAFM to FM state, and at high temperaturesT.Tc—a revers-ible albeit slightly hysteretic PM-FM transition. Magneto-striction of about 2310−4 is clearly seen to accompany thePM-FM transition(upper inset) in accordance with the dataof Ref. 19. The 1/x data just aboveTc show a tendency forAFM interactions that competes with FM ordering at inter-mediate temperatures.The irreversible metamagnetic AFM-FM transition isshown to be steplike(Fig. 2) after zero-field cooling. Wehave observed that the step location depends on the sweeprate of the following magnetic field: the smaller the sweeprate, the larger the field value needed to realize the transition.For the Sm0.5Sr0.5Mn18O3 sample at the rateø250 Oe/s thetransition becomes smooth. This shows that the steplike tran-sition is not an intrinsic property of a compound. Two ques-tions arise at this point:(i) how sharp are these steps and(ii )is M a function of the magnetic field along all the steps or isonly the start of the transition triggered by the magneticfield?To resolve these problems we have studied theMsHdsteps at different sweep rates with our high-speed experimen-tal setup with 10ms resolution. The results shown in theinset to Fig. 2 demonstrate the finite width of the transitionof the order of 1 ms. Note that this curve is the same fordifferent sweep rates200–3000 Oe/sd. Being triggered, thetransition will complete in a definite time independent on thefurther changes of theH. In the case of Sm0.5Sr0.5Mn18O3,this time scale is approximately 10 times higher(not shown).Thus, our samples with a relatively small difference in Srcontent exhibit a factor of 10 difference in the transitiontime. This fact cannot be easily reconciled with the scenarioof a martensitic transition because the microstructure of bothsamples is identical. Moreover, a distribution of avalanchesin martensitic transformations has usually no characteristictime scales20 unlike our observations.To further elucidate the origin of such sharp transitions,we have checked the effects of the cooling rate on the low-temperature magnetic state(Fig. 3). The quenched-in disor-der should be strongly affected by the cooling rate. In thecase of martensitic transformation,20 a slow cooling rateleads to a low defect concentration so that the strains arereleased via large avalanches. On the other hand, fast coolingresults in a large number of defects and thus leads to a se-quence of many small avalanches. However, as we will dis-cuss below, the behavior observed in our experiments withdifferent cooling rates shows the opposite tendency. This isin our opinion a strong argument against the interpretation ofthe jumps as a consequence of martensitic phenomena.Two cooling rates were used in our experiments. In thefirst, slow cooling, the sample was cooled at the rate of1 K/min from 300 K to 5 K in zero applied field for trans-port and specific heat measurements and 100 Oe for magne-tization experiments. In the second, fast cooling regime, thecooling rate was 10 K/min for resistivity and specific heatmeasurements and approximately 20 K/min for magnetiza-tion. Usually, no specific information is provided in the lit-erature on the employed cooling rate in manganite research,and we assume that most results are obtained using a rela-tively fast cooling rate.Two key points should be noted in the data of Fig. 3. Thefirst is a huge thermal hysteresis for the data obtained onheating and cooling, which is generally considered to be afingerprint of a first order phase transition. The second is astriking difference in the low-temperature states of theFIG. 1. Magnetization loops for Sm0.55Sr0.45MnO3 recorded af-ter zero-field cooling from room temperature. The data for the firstincrease of the magnetic field are shown in the first quadrant andmarked with bold arrows if different from stable curves(III quad-rant). T=5 K (h), 55 K (s), 120 K (n), and 140 K(,). The upperleft inset shows magnetostriction at 120 K, the lower right one pre-sents a high-temperature tail of inverse susceptibility atm0H=0.1 T.FIG. 2. The dependence of the magnetization jump on the mag-netic field sweep rate for Sm0.55Sr0.45Mn18O3 (a) andSm0.5Sr0.5Mn18O3 (b) at T=5 K. Inset shows the time dependenceof the magnetization during the jump. This dependence is the samefor the sweep rates in the range 200–3000 Oe/s.BRIEF REPORTS PHYSICAL REVIEW B70, 212411(2004)212411-2fast- and slow-cooled samples. For the former, we observe alow-magnetization state with a relatively high resistivity. Forthe latter, the magnetization is 10 times higher and the resis-tivity is smaller. The additional linear term in the specificheat appears for the fast cooled sample as shown in the insetto Fig. 3(a). These differences diminish upon heating anddisappears atT<45 K.The low-temperature magnetization and resistivity loopsafter slow and fast cooling(Fig. 4) have qualitatively differ-ent behavior. The steplike transition inMsHd andrsHd existsonly for fast cooled samples, whereas this transformation issmooth in slow cooled samples. Comparison of the data ofFigs. 4(a) and 4(b) shows that the fast-cooled samples havesignificantly larger resistivity even at the same value ofM[compare, for instance,rsH=0.5,1.1 Td]. This is an evidencefor a quenched disorder in fast-cooled samples(cf. Ref. 21).The other evidence of an additional disorder is shown in theinset to Fig. 3(a). The fitting of the temperature dependenceof the specific heat is the same for both cooling rates exceptan additional linear term of the order of 20% in the fast-cooled sample.(Note, that conductivity in this case is evenlower and the electron term could not be the origin of thischange.) Corresponding extra entropyDS=0.25J/K/mol isof the same order as the entropy change upon PM-FM tran-sition s,0.6 J/K/mold, thus we believe this extra linear termto have essentially magnetic origin, possibly spin-glass-liketype.22 However, there is almost no additional strain(lessthan 10−5) in the fast-cooled sample and the magnetostrictionis smooth for both histories. This, together with the oppositedependence of the behavior of our samples on the coolingrate, mentioned above, in our opinion rules out the descrip-tion of these phenomena as a consequence of a martensiticnature of the transition.Upon cooling, the AFM-FM competition may result in astrongly disordered magnetic state, which has an excess spe-cific heat and enhanced magnetocaloric effect.23 Ferromag-netic ordering with the external magnetic field would lead tothe reduction of this extra entropy. In this case, the localrelease of the frozen entropy may result in the avalanchelikeoverheating of the sample because the higher the temperaturethe more tendency to ferromagnetism is observed at low tem-peratures(cf. the data for 5 and 55 K in Fig. 1). So, both themagnetization and resistivity change in a jumplike fashion.Such effect was observed recently14 on the steplike transi-tion. This scenario assumes the time scale of the transition tobe inversely proportional to the thermal conductivity of thesample. This is exactly the case if one comparesSm1−xSrxMn18O3 with x=0.45 and 0.5. The resistivity ofSm0.5Sr0.5Mn18O3 is at least four orders of magnitudehigher18 so that the thermal conductivity should be lower. Werecall that the observed time scale of the jump forSm0.5Sr0.5Mn18O3 is 10 times larger than forSm0.55Sr0.45Mn18O3.Summarizing, we studied the magnetization and resistiv-ity jumps in Sm1−xSrxMn18O3, especially their dependenceon the cooling rate. The slows1 K/mind cooled samplesdemonstrate a smooth AFM-FM transition upon increase ofthe magnetic field, in contrast to the fast,10 K/mindcooled samples where this transition is steplike with a char-acteristic time scale of 1 ms. The results obtained(theFIG. 3. The temperature dependences of the low-fields0.01 Tdmagnetization (a) and zero-field resistivity (b) ofSm0.55Sr0.45Mn18O3 obtained for different temperature histories:(s) slow cooling,(P) heating after slow cooling, and(n) heatingafter fast cooling. Insets show the temperature dependence of thespecific heat(a) and resistivity(b) of sNdEud0.55Sr0.45Mn18O3 forthe same temperature histories.FIG. 4. Magnetization (a) and resistivity (b) loops forSm0.55Sr0.45Mn18O3 recorded at 5 K after slow and fast cooling inzero field, which demonstrate the absence of jumps for slowlycooled samples. The inset shows a minor effect of the cooling rateon the magnetostriction. Here the parabolic increase is caused bythe magnetoresistance of the gauge itself.BRIEF REPORTS PHYSICAL REVIEW B70, 212411(2004)212411-3dependence of the jumps on the cooling rate; the constanttime scale of the jumps, independent on the field-sweep rate;the behavior of specific heat; the absence of noticeable mag-netostriction) disagree with the often used interpretation thatthe magnetization steps originate from the strain release at amartensitic transition. We suggest that the frozen disorderand the associated entropy is the origin of an excess specificheat which is released in an avalanchelike way upon apply-ing a magnetic field, resulting in a heat burst in the sampleand in steps in the magnetization and resistivity.This study was supported by the Netherlands Organiza-tion for the Advancement of Pure Research(NWO) and IN-TAS project(01-2008).*Corresponding author. Email address: kalinov@vei.ru1E. Stryjewski and N. Giordano, Adv. Phys.26, 487 (1977).2J. M. D. Coey, M. 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Magnetic field induced steplike changes in magnetization and resistivity of Sm1−xSrxMnO3 manganites were studied. A strong dependence of these features on the cooling rate was observed. Magnetostriction, however, does not show the presence of large strain in our samples. From all these features we can rule out the conventional explanation of magnetization jumps as a consequence of martensitic transition. We propose instead that quenched by fast cooling disorder leads to the formation of an inhomogeneous metastable state and to subsequent magnetization jumps.

Fisher, L.M.,

Kalinov, A.V.,

Voloshin, I.F.,

Babushkina, N.A.,

Khomskii, D.I.,

Zhang, Y.,

Palstra, T.T.M.,

University of Groningen Digital Archive

Quenched disorder induced magnetization jumps in (Sm,Sr)MnO$_3$

Quenched disorder induced magnetization jumps in (Sm,Sr)MnO $_3$

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Quenched disorder induced magnetization jumps in (Sm,Sr)MnO3_33​

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ARTS repository - University of Groningen

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Quenched disorder induced magnetization jumps in (Sm,Sr)MnO $_3$