74 research outputs found
Stretched exponential behavior in remanent lattice striction of a (La,Pr)SrMnO bilayer manganite single crystal
We have investigated the time dependence of remanent magnetostriction in a
(La,Pr)SrMnO single crystal, in order to examine
the slow dynamics of lattice distortion in bilayered manganites. A competition
between double exchange and Jahn-Teller type orbital-lattice interactions
results in the observed lattice profile following a stretched exponential
function. This finding suggests that spatial growth of the local lattice
distortions coupled with e-electron orbital strongly correlates with the
appearance of the field-induced CMR effect.Comment: 3 figure
Anomalous pressure effect on the remanent lattice striction of a (La,Pr)SrMnO bilayered manganite single crystal
We have studied the pressure effect on magnetostriction, both in the
-plane and along the c-axis, of a (La,Pr)SrMnO
bilayered manganite single crystal over the temperature region where the
field-induced ferromagnetic metal (FMM) transition takes place. For comparison,
we have also examined the pressure dependence of magnetization curves at the
corresponding temperatures. The applied pressure reduces the critical field of
the FMM transition and it enhances the remanent magnetostriction. An anomalous
pressure effect on the remanent lattice relaxation is observed and is similar
to the pressure effect on the remanent magnetization along the c-axis. These
findings are understood from the view point that the double-exchange
interaction driven FMM state is strengthened by application of pressure.Comment: 7 pages,7 figure
Colossal electroresistance and colossal magnetoresistive step in paramagnetic insulating phase of single crystalline bilayered manganite(LaPr)SrMnO
We report a significant decrease in the low-temperature resistance induced by
the application of an electric current on the -plane in the paramagnetic
insulating (PMI) state of
(LaPr)SrMnO. A colossal
electroresistance effect attaining -95% is observed at lower temperatures. A
colossal magnetoresistive step appears near 5T at low temperatures below 10K,
accompanied by an ultrasharp width of the insulator-metal transition. Injection
of higher currents to the crystal causes a disappearance of the steplike
transition. These findings have a close relationship with the presence of the
short-range charge-ordered clusters pinned within the PMI matrix of the crystal
studied.Comment: 4 pages 3 figure
Steplike Lattice Deformation of Single Crystalline (LaPr)SrMnO Bilayered Manganite
We report a steplike lattice transformation of single crystalline
(LaPr)SrMnObilayered manganite
accompanied by both magnetization and magnetoresistive jumps, and examine the
ultrasharp nature of the field-induced first-order transition from a
paramagnetic insulator to a ferromagnetic metal phase accompanied by a huge
decrease in resistance. Our findings support that the abrupt magnetostriction
is closely related to an orbital frustration existing in the inhomogeneous
paramagnetic insulating phase rather than a martensitic scenario between
competing two phases.Comment: 5 pages,4figures, v4: figures are changed, in press in Phys.Rev.Let
Magnetic order in double-layer manganites (La(1-z)Pr(z))1.2Sr1.8Mn2O7: intrinsic properties and role of the intergrowths
We report on an investigation of the double-layer manganite series
(La(1-z)Pr(z))1.2Sr1.8Mn2O7 (0 <= z <= 1), carried out on single crystals by
means of both macroscopic magnetometry and local probes of magnetism (muSR,
55Mn NMR). Muons and NMR demonstrate an antiferromagnetically ordered ground
state at non-ferromagnetic compositions (z >= 0.6), while more moderate Pr
substitutions (0.2 <= z <= 0.4) induce a spin reorientation transition within
the ferromagnetic phase.
A large magnetic susceptibility is detected at {Tc,TN} < T < 250K at all
compositions. From 55Mn NMR spectroscopy, such a response is unambiguously
assigned to the intergrowth of a ferromagnetic pseudocubic phase
(La(1-z)Pr(z))(1-x)Sr(x)MnO3, with an overall volume fraction estimated as
0.5-0.7% from magnetometry. Evidence is provided for the coupling of the
magnetic moments of these inclusions with the magnetic moments of the
surrounding (La(1-z)Pr(z))1.2Sr1.8Mn2O7 phase, as in the case of finely
dispersed impurities. We argue that the ubiquitous intergrowth phase may play a
role in the marked first-order character of the magnetic transition and the
metamagnetic properties above Tc reported for double-layer manganites.Comment: 11 pages, 9 figures. Submitted to Phys. Rev.
Effect of suppression of local distortion on magnetic, electrical and thermal transport properties of Cr substituted bi-layer manganite LaSrMnO
We have investigated magnetic, electrical and thermal transport properties
(Seebeck effect and thermal conductivity) of
LaSrMnCrO polycrystalline samples (=0.1, 0.2, 0.4
and 0.6). The Cr substitution for Mn sites causes a removal of
orbital of -electron resulting in a volume shrinkage of
lattice. Magnetic measurements reveal the appearance of a glassy behavior for
Cr-doped samples, accompanied by both a collapse of the A-type
antiferromagnetic structure and the growth of ferromagnetic clusters. Cr-doping
effect on electrical transport strongly enhances an insulating behavior over a
wide range of temperature, while it suppresses a local minimum of
thermoelectric power at lower temperatures. The phonon thermal conduction
gradually rises with increasing Cr content, which is contradictory to a typical
impurity effect on thermal conductivity. We attribute this to a suppression of
local lattice distortion through the introduction of Jahn-Teller inactive ions
of Cr.Comment: 8 pages, 9figure
Anisotropic phonon conduction and lattice distortions in CMR-type bilayer manganite (LaPr)SrMnO (z=0,0.2,0.4 and 0.6) single crystals
We have undertaken a systematic study of thermal conductivity as a function
of temperature and magnetic field of single crystals of the compound
(LaPr)SrMnO for (Pr) =0.2,0.4. and
0.6. The lattice distortion due to Pr-substitution and anisotropic thermal
conductivity in bilayer manganites are discussed on the basis of different
relaxation models of local lattice distortions in metal and insulating states
proposed by Maderda et al. The giant magnetothermal effect is scaled as a
function of magnetization and discussed on the basis of a systematic variation
of the occupation of the -electron orbital states due to Pr-substitution.Comment: 7 pages, 6 figures, in press in Phys.Rev.
Effect of pressure on steplike magnetostriction of single crystalline (LaPr)SrMnO bilayered manganite
e report the effect of pressure on the steplike magnetostriction of single
crystalline bilayered manganite (LaPr)1.2Sr1.8Mn2O8, for our understandings of
the ultrasharp nature of the field-induced first-order transition from a
paramagnetic insulator to a ferromagnetic metal phase. The application of
pressure suppresses a steplike transformation and causes a broad change in the
magnetostriction. The injection of an electric current to the crystal also
weakens the steplike variation in both the magnetostriction and
magnetoresistance. The stabilization of ferromagnetic interaction or the
delocalization of charge carriers is promoted with the applied pressure or
applied current, resulting in the suppressed steplike behavior. Our findings
suggest that the step phenomenon is closely related to the existence of
localized carriers such as the short-range charge-orbital ordered clusters.Comment: 5 pages,4 figure
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