The complex ac dynamic magnetic susceptibility was used to study the mictomagnetic-like behavior in
polycrystalline Cd0:87Cr1:93V0:06Se4 spinel. The temperature dependences of the zero field in-phase (real part) and out-of-phase (imaginary part) components of fundamental susceptibility measured at the oscillating field
Hac = 0:5 Oe and at the constant frequency of 125 Hz are characteristic for the mictomagnetic order. These
results well correlate with the anomalies in the second and third harmonics of the ac susceptibility indicating the
cluster glass

Duda, Henryk

Groń, Tadeusz

Krok-Kowalski, Józef

Malicka, Ewa

Pacyna, A. W.

Zawisza, Beata

Acta Physica Polonica A

English

Repozytorium Uniwersytetu Śląskiego RE-BUŚ

             Title: Mictomagnetic order in Cd0.87Cr1.93V 0.06Se4 semiconductor  Author: Tadeusz Groń, Ewa Malicka, Beata Zawisza, Henryk Duda, Józef Krok-Kowalski, A. W. Pacyna  Citation style: Groń Tadeusz, Malicka Ewa, Zawisza Beata, Duda Henryk, Krok-Kowalski Józef, Pacyna A. W. (2011). Mictomagnetic order in Cd0.87Cr1.93V 0.06Se4 semiconductor. "Acta Physica Polonica A" (Vol. 119, nr 5 (2011), s. 714-716).  Vol. 119 (2011) ACTA PHYSICA POLONICA A No. 5XXXIX “Jaszowiec” International School and Conference on the Physics of Semiconductors, Krynica-Zdrój 2010Mictomagnetic Order in Cd0.87Cr1.93V0.06Se4 SemiconductorT. Grońa, E. Malickab, B. Zawiszab, H. Dudaa, J. Krok-Kowalskiaand A.W. PacynacaUniversity of Silesia, Institute of Physics, Uniwersytecka 4, 40-007 Katowice, PolandbUniversity of Silesia, Institute of Chemistry, Szkolna 9, 40-006 Katowice, PolandcThe Henryk Niewodniczański Institute of Nuclear Physics, Polish Academy of SciencesE. Radzikowskiego 152, 31-342 Kraków, PolandThe complex ac dynamic magnetic susceptibility was used to study the mictomagnetic-like behavior inpolycrystalline Cd0.87Cr1.93V0.06Se4 spinel. The temperature dependences of the zero field in-phase (real part)and out-of-phase (imaginary part) components of fundamental susceptibility measured at the oscillating fieldHac = 0.5 Oe and at the constant frequency of 125 Hz are characteristic for the mictomagnetic order. Theseresults well correlate with the anomalies in the second and third harmonics of the ac susceptibility indicating thecluster glass.PACS: 72.80.Jc, 75.50.Pp, 75.50.Dd1. IntroductionThe electrical and magnetic investigations carried outon the polycrystalline spinels with the general chemi-cal formula CdxCryVzSe4 (where z = 0.06, 0.12, 0.24,and 0.31) revealed semiconducting and ferromagneticproperties with an almost constant Curie temperatureTC = 128 K and a Curie–Weiss temperature (θCW) de-creasing from 160 K for z = 0.06 to 140 K for z = 0.31 [1].The Cd0.87Cr1.93V0.06Se4 spinel pays special attentionbecause it showed a change of thermopower sign from pto n at 243 K and a step-like structure of the electri-cal conductivity (SLS EC). This structure has been ex-plained in a framework of the impurity conduction andhopping conduction as well as with the formation of fer-romagnetic clusters in the Cr band, which is partly im-perfect by cation deficiency from one side and weaklydiluted by the V3+ ions forming the 3d2t22ge0g band fromthe other [1]. The SLS EC effect was first discoveredin the Zn1−xGa2x/3Cr2Se4 spinel system for the sin-gle crystal containing 3% Ga ions [2] and next in theCdCr2−xGaxSe4 spinel system for the single crystal con-taining 1.5% Ga ions occupied in both cases the oc-tahedral sites [3]. Pure CdCr2Se4 combines a p-typesemiconducting behaviour of the Arrhenius type andferromagnetic order via superexchange interaction withTC = 142 K and θCW = 190 K [4].The main purpose of the present work is an attemptto study in more detail a magnetic order and correlateit with the SLS EC phenomenon of the polycrystallineCd0.87Cr1.93V0.06Se4.2. Experimental detailsPowder sample of the Cd0.87Cr1.93V0.06Se4 spinel wasobtained by a ceramic method [5]. The X-ray diffractionand a precise atomic content determination were donewith the aid of the SIEMENS D5000 diffractometer andthe energy-dispersive X-ray spectrometry (EDXRF), re-spectively, showing a single-phase material with a cu-bic spinel structure (Fd3m) and a lattice parameter of1074.70 pm. The composition studied in this paper isthe same as reported in Ref. [1].The dynamic ac magnetic susceptibilities using a LakeShore 7225 ac susceptometer were measured in the zero--field-cooling mode. The in-phase χ′1 and out-of-phaseχ′′1 components of the ac fundamental susceptibility wererecorded in the temperature range 4.2–150 K simulta-neously as a function of temperature in an oscillatingfield Hac = 0.5 Oe with frequency of 125 Hz and in thedifferent external magnetic fields Hdc changing from 0to 5 kOe. The signals of the second (χ2) and third (χ3)harmonics associated with nonlinear susceptibilities weredetected as a function of temperature using an oscillatingfield of 1 Oe without the applied external magnetic field.3. Results and discussionFigure 1 shows the temperature dependence of the dy-namic magnetic susceptibility recorded at Hac = 0.5 Oewith frequency f = 125 Hz. ForHdc = 0 the χ′1(T ) showsa linear increase up to 50 K, the paraprocess in the range50–100 K, a constant value in the range 100–125, and asharp drop at TC = 128 K. With increasing Hdc from100 to 5 kOe the χ′1 intensity suppresses, TC shifts tohigher temperatures and simultaneously a broad humpoccurs with a maximum shifting to lower temperatures.The χ′′1(T ) reveals the largest energy lost in the range4.2–50 K with maximum at 20 K slightly shifting to lowertemperatures as Hdc increases. The χ′1(T ) dependenceseems to be attributed to the cluster glass-like behaviour(714)Mictomagnetic Order in Cd0.87Cr1.93V0.06Se4 Semiconductor 715Fig. 1. In-phase χ′1 and out-of-phase χ′′1 components ofzero field fundamental susceptibility vs. temperature Trecorded at Hac = 0.5 Oe with f = 125 Hz for externalmagnetic fields Hdc changing from 0 to 5 kOe.Fig. 2. In-phase χ′2 and out-of-phase χ′′2 componentsof second harmonics of zero field susceptibility vs. tem-perature T recorded at Hac = 1 Oe with f = 80 Hz.where the local correlations of the magnetic ions (as pairs,triplets, and so forth) are coupled by direct exchange [6].Figures 2 and 3 show the higher harmonics of dynamicsusceptibility, i.e. the second χ2(T ) and third χ3(T )which have one feature in common: they vanish aboveTC in accordance with the simple molecular field the-Fig. 3. In-phase χ′3 and out-of-phase χ′′3 componentsof third harmonics of zero field susceptibility vs. tem-perature T recorded at Hac = 1 Oe with f = 125 Hz.Fig. 4. In-phase χ′1 and out-of-phase χ′′1 componentsof zero field fundamental susceptibility vs. tempera-ture T for CdCr2Se4 recorded at Hac = 1 Oe withf = 125 Hz for external magnetic fields Hdc changingfrom 0 to 1 kOe.ory [7]. The in-phase second χ′2 and third χ′3 harmonicschange their signs in opposite way both at 15 K and TC.Next, the out-of-phase second χ′′2 and third χ′′3 harmon-ics reveal the energy dissipation at TC and 15 K, respec-tively. The negative value of the real part and the posi-tive value of the imaginary part of the 2nd harmonic ofthe ac magnetic susceptibility (Fig. 2) are the experimen-tal signatures of the spin glass state. Here, the partiallydestroyed ferromagnetic (via superexchange) interactionmay result purely from the geometry or topology of thelattice (known as the geometric frustration). This is con-716 T. Groń et al.nected mainly with the V substitution, because the V ionhas a larger radius (64 pm) and smaller magnetic momentin comparison with the Cr one (61.5 pm [8]).Figure 4 shows the temperature dependence of the dy-namic magnetic susceptibility of the CdCr2Se4 matrixrecorded at Hac = 1 Oe with frequency f = 125 Hz forcomparison. ForHdc = 0 the χ′1 reveals typical ferromag-netic order and the χ′′1 oscillates close to zero indicatinga lack of the energy dissipation. A striking differencebetween the χ′1(T ) dependences in Figs. 1 and 4 is evi-dent. On the other hand, χ′1 shows a peak near the Curietemperature when heating the sample in a fixed (small)magnetic field [9]. This is characteristic for the Hopkin-son effect in the samples consisting of fine powders ofsingle domain particles [10, 11].4. ConclusionsIt is clearer now that the mictomagnetic order in theCd0.87Cr1.93V0.06Se4 can occur and the small groupsaround the V ions coexist as the spin-glass entities em-bedded in a ferromagnetic matrix. From the other hand,Monte Carlo simulations carried out on large samplesof two-dimensional and three-dimensional Ising modelsconfirmed that for critical concentrations (i.e., for thefraction of negative interactions and for the fraction offrustrated spins) the magnetic defect structures (clusters)appear leading to the unusual changes of the physicalproperties [12]. Thus, a mictomagnetic order, i.e. a clus-ter glass maybe the main reason of the appearance of astep-like structure of the electrical conductivity experi-mentally observed in the studied spinel.One can conclude that a presence of a few percent ofthe V ions in the octahedral positions makes easier arapid increase in conductivity with increasing tempera-ture as well as a dissolution of the ferromagnetic spinclusters on going towards the paramagnetic limit.AcknowledgmentsThis work is partly founded from science grant No. NN204 145938.References[1] T. Groń, H. Duda, E. Malicka, B. Zawisza, J. Krok--Kowalski, A.W. Pacyna, Acta Phys. Pol. A 116, 969(2009).[2] T. Groń, E. Malicka, I. Okońska-Kozłowska,A. Waśkowska, in: Ferrites: Proc. Eight Int. Conf.on Ferrites, The Japan Society of Powder and Pow-der Metallurgy, Kyoto 2000, p. 211.[3] T. Groń, A. Krajewski, J. Kusz, E. Malicka,I. Okońska-Kozłowska, A. Waśkowska, Phys. Rev. B71, 035208 (2005).[4] P.K. Baltzer, H.W. Lehmann, M. Robbins, Phys. Rev.Lett. 15, 493 (1965).[5] I. Okońska-Kozłowska, J. Krok, Z. Anorg. Allg.Chem. 447, 235 (1978).[6] C.M. Hurd, Contemp. Phys. 23, 469 (1982).[7] T. Hashimoto, A. Sato, Y. Fujiwara, J. Phys. Soc.Jpn. 35, 81 (1973).[8] R.D. Shannon, Acta Crystallogr. A 32, 751 (1976).[9] J. Hopkinson, Proc. R. Soc. Lond. 48, 1 (1890).[10] O. Popov, M. Mikhov, J. Magn. Magn. Mater. 75,135 (1988).[11] O. Popov, P. Rachev, M. Mikhov, F. Calderon,J.L. Sanchez, F. Leccabue, J. Magn. Magn. Mater.99, 119 (1991).[12] S. Kirkpatrick, Phys. Rev. B 16, 4630 (1977).

Mictomagnetic order in Cd0.87Cr1.93V 0.06Se4 semiconductor

https://rebus.us.edu.pl/bitstream/20.500.12128/8202/1/Gron_Mictomagnetic_order_in_Cd0.87Cr1.03V0.06Se4.pdf

Mictomagnetic order in Cd0.87Cr1.93V 0.06Se4 semiconductor

Abstract

Similar works

Full text

Available Versions

Repozytorium Uniwersytetu Śląskiego RE-BUŚ