An antiferromagnetic order with a Néel temperature TN = 17:5 K, a strong ferromagnetic exchange evidenced
by a positive Curie Weiss temperature  CW = 77:3 K, the fuzzy peaks in the real component of susceptibility x′
(T) and the disappearance of the second critical  eld were established. The curvature of speci c heat C(T) and
C(T)=T in surrounding of TN indicated a broad peak, characteristic for the system with inhomogeneous magnetic
state (spin-glass-like phase). The calculated magnetic entropy showed the value of S(T)   1 J/(mol K) which is
extremely small; i.e., much lower than the magnetic contribution Rln(2S + 1) = 11:52 J/(mol K) calculated for
the spin 3/2

Gagor, A.

Goraus, Jerzy

Groń, Tadeusz

Malicka, Ewa

Mydlarz, T.

Pacyna, A.

Ślebarski, Andrzej

Acta Physica Polonica A

English

Repozytorium Uniwersytetu Śląskiego RE-BUŚ

             Title: Specific heat and magnetic properties of single-crystalline (Zn0.925In0.054)[Cr1.84In0.152]Se-4 semiconductor  Author: Ewa Malicka, Tadeusz Groń, A. Pacyna, Andrzej Ślebarski, Jerzy Goraus, A. Gagor, T. Mydlarz  Citation style: Malicka Ewa, Groń Tadeusz, Pacyna A., Ślebarski Andrzej, Goraus Jerzy, Gagor A., Mydlarz T. (2012). Specific heat and magnetic properties of single-crystalline (Zn0.925In0.054)[Cr1.84In0.152]Se-4 semiconductor. "Acta Physica Polonica A" (Vol. 122, nr 6 (2012), s. 1108-1110).  Vol. 122 (2012) ACTA PHYSICA POLONICA A No. 641th Jaszowiec International School and Conference on the Physics of Semiconductors, Krynica-Zdrój 2012Specic Heat and Magnetic Properties of Single-Crystalline(Zn0:925In0:054)[Cr1:84In0:152]Se4 SemiconductorE. Malickaa, T. Gro«b, A.W. Pacynac, A. lebarskib, J. Gorausb, A. G¡gordand T. MydlarzeaInstitute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice, PolandbInstitute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, PolandcThe Henryk Niewodnicza«ski Institute of Nuclear Physics, Polish Academy of SciencesE. Radzikowskiego 152, 31-342 Kraków, PolanddInstitute of Low Temperature and Structure Research, Polish Academy of SciencesP.O. Box 1410, 50-950 Wrocªaw, PolandeInternational Laboratory of High Magnetic Fields and Low TemperaturesGajowicka 95, 53-529 Wrocªaw, PolandAn antiferromagnetic order with a Néel temperature TN = 17:5 K, a strong ferromagnetic exchange evidencedby a positive CurieWeiss temperature CW = 77:3 K, the fuzzy peaks in the real component of susceptibility0(T ) and the disappearance of the second critical eld were established. The curvature of specic heat C(T ) andC(T )=T in surrounding of TN indicated a broad peak, characteristic for the system with inhomogeneous magneticstate (spin-glass-like phase). The calculated magnetic entropy showed the value of S(T )  1 J/(mol K) which isextremely small; i.e., much lower than the magnetic contribution R ln(2S + 1) = 11:52 J/(mol K) calculated forthe spin 3/2.PACS: 65.40.Ba, 75.50.Ee, 75.50.Pp1. IntroductionIt is well known in literature that the p-type semicon-ducting [1] antiferromagnet [2] ZnCr2Se4 diluted by thenonmagnetic ions shows the eects of the site disorder,lattice frustration and random distribution of spin inter-actions [36], which create novel potential applications inthe spin-based electronic technology. Recently, we havepresented the specic heat data for the series of ZnCr2Se4substituted by Al, Ga, In, or Ce [5, 6]. As the main con-clusion we observed the following behaviours: the antifer-romagnetic transition at TN with a sharp peak of -typein the specic heat was strongly shifted to much lowertemperatures in the applied magnetic elds, and the mag-netic entropy at TN is only about 10% of the full mag-netic entropy expected for the complete alignment of theCr magnetic moments. The rst observation indicates onthe second order phase transition, while the strong reduc-ing of the entropy was explained as result of the spin uc-tuations generated much above TN. Spectacular loweringof the saturation magnetic moment toMs = 1:04 B/f.u.at 4.2 K and at 136 kOe for (Zn0:84In0:1)[Cr1:78In0:14]Se4was most unexpected [5, 6].The present contribution reports magneticand specic heat measurements for almost sto-ichiometric (Zn0:925In0:054)[Cr1:84In0:152]Se4 tocompare with those ones for non-stoichiometric(Zn0:84In0:1)[Cr1:78In0:14]Se4 [6], having similar compo-sition.2. Experimental detailsThe (Zn0:925In0:054)[Cr1:84In0:152]Se4 single crystal wasobtained by a chemical vapour transport reaction usinganhydrous chromium chloride CrCl3 (purity 95%) as atransporting agent. Chemical composition of the sin-gle crystal was determined nondestructively by energy--dispersive X-ray uorescence spectrometry (EDXRF).A single-crystal X-ray data collection was performed withKuma KM4CCD diractometer equipped with CCD de-tector and using Mo K radiation. Magnetization aswell as dc and ac magnetic susceptibility with real (0)and imaginary (00) components were measured in thezero-eld-cooled mode using a vibrating sample magne-tometer with a step motor at 4.2 K and in applied mag-netic elds up to 150 kOe and a Lake Shore 7225 ac sus-ceptometer up to 60 kOe in the temperature range 4.2100 K, respectively. Specic heat was measured with aQuantum Design Physical Properties Measurement Sys-tem (QD-PPMS) with heat capacity option in tempera-ture range 1.824 K and at magnetic eld up to 50 kOe.3. Results and discussion(Zn0:925In0:054)[Cr1:84In0:152]Se4 crystallizes in the cu-bic spinel structure with the space group symmetryFd3m (No. 227). The In3+ substitution for Zn2+ re-vealed the appearance of the cation vacancies with thetotal cation deciency of 2.9% as well as the large bondfrustration resulting from the random distribution of(1108)Specic Heat and Magnetic Properties . . . 1109Cr/ZnSe and Zn/InSe bonds both in the tetra- (A)and octahedral (B) sites, although this spinel is almoststoichiometric. The cubic lattice parameter a equals to10.5138(5) Å and it is larger in the comparison to thematrix ZnCr2Se4 with a = 10:497(1) Å [6]. It may beattributed to the presence of In3+ in B site. The moststable and convergent renements were obtained for theatom positions and SOFs presented in Table.TABLEAnion parameter (u), site occupation factors (SOF)and equivalent isotropic displacement parameters (Uiso)at 295 K.Atom Wycko position SOFUiso[102 Å2]Zn/InCr/InSe8a (1/8, 1/8, 1/8)16d (1/2, 1/2, 1/2)32e (u, u, u)u = 0:25951(2)0.926(2)/0.054(2)0.918(3)/0.076(2)1.01.19(2)1.27(2)1.03(1)Fig. 1. Magnetization M vs. magnetic eld 0H at4.2 K. Inset: magnetic susceptibilities vs. temperature(T ),  1 (T ), and 1=(   0) at Hdc = 1 kOe. Thesolid (red) line (T   )=C indicates a CurieWeiss be-haviour.Magnetization and magnetic susceptibility measure-ments are presented in Figs. 13. The saturation mag-netic moment Ms = 3:91 B/f.u. at 4.2 K. An antifer-romagnetic order with a Néel temperature TN = 17:5 Kand a strong ferromagnetic exchange evidenced by a pos-itive CurieWeiss temperature CW = 77:3 K was es-tablished. The temperature independent component ofsusceptibility 0 = 7:509  10 6 cm3/g obtained fromthe tting procedure [7] of the CurieWeiss law sug-gests the temperature-independent contributions of or-bital and Landau diamagnetism, Pauli and Van Vleckparamagnetism, as they cannot be separated. Becausethe ZnCr2 xInxSe4 spinels are semiconductors [8], theLandau and Pauli contributions can be neglected. Thus,the positive value of 0 can come from the Van Vleckcontribution, which usually arises from that part of theFig. 2. Ac magnetic susceptibility, ac, vs. static mag-netic eld H recorded at internal oscillating magneticeld Hac = 1 Oe with internal frequency f = 120 Hztaken at dierent temperatures. The critical elds Hc1and Hc2 are indicated by arrows.Fig. 3. Real 0 and imaginary 00 components of acmagnetic susceptibility vs. temperature T recorded atHac = 1 Oe with f = 120 Hz taken at dierent externalmagnetic elds Hdc.orbital moment which has been admixed back into theground state by the orbital Zeeman eect [9]. ac(H) inFig. 2 shows a slight shift of the rst critical eld Hc1 andthe disappearance of the second critical eldHc2 with thetemperature. The fuzzy peak at Tm = 40 K in 0(T ) andthe 00(T ) signal oscillating around zero depicted in Fig. 3indicate the weak ferromagnetic order persisting in theparamagnetic region.(Zn0:925In0:054)[Cr1:84In0:152]Se4 exhibits similar elddependence of TN and strong lowering of entropy S(T ) incomparison with (Zn0:84In0:1)[Cr1:78In0:14]Se4 [6], how-1110 E. Malicka et al.Fig. 4. Specic heat, C, vs. temperature T taken atdierent external magnetic elds.Fig. 5. Specic heat, C, vs. temperature T taken inzero magnetic eld. Cph is the Debye t and C =C   Cph.ever, it has quite dierent curvature of C(T ) and C(T )=Tin surrounding of TN. Namely, instead of the sharp-type anomaly we observed a broad peak, character-istic of the system with inhomogeneous magnetic state(spin-glass-like phase). From this point of view, this com-pound seems to be interesting. In Fig. 4 we present thespecic heat vs. temperature at dierent magnetic elds.The maximum in the C(T )=T data (not shown in this pa-per) is at 15.1 K for the magnetic eld 0H = 0, and lin-early decreases with increasing eld; e.g., for 0H = 5 T,Tmax  2:6 K. In Fig. 5 we present the C(T ) data ob-tained at 0H = 0, and the magnetic contribution Cwhen C(T ) are subtracted by the calculated phonon con-tribution Cph = T 3.The calculated magnetic entropy per formula unitshown in Fig. 6, S(T ) =R T0C(T )T dT is at TN only 2 J/(mol K). The value of S  1 J/(mol K) calculatedper Cr ion is extremely small; i.e., much lower than themagnetic contribution R ln(2S + 1) = 11:52 J/(mol K)calculated for the spin 3/2. So much strongly reducedmagnetic entropy S(T ) can in part result from the spinuctuations observed above TN, however this is not theonly one reason. In the similar compounds (cf. Ref. [4]and [6]) the entropy is also strongly reduced, however,the value of S(T ) per one Cr atom was measured about4 times larger. The reason of the strong S(T ) anomaly for(Zn0:925In0:054)[Cr1:84In0:152]Se4 single crystalline sam-ple seems well not to be understood, although the samplestoichiometry and the structural defects play an essentialrole in this case.Fig. 6. Entropy S per formula unit vs. temperature Tin zero magnetic eld.References[1] F.K. Lotgering, in: Proc. Int. Conf. on Magnetism,Nottingham, ed. L.F. Bates, Institute of Physics, Lon-don 1965, p. 533.[2] R. Plumier, J. Phys. (Paris) 27, 213 (1966).[3] E. Malicka, T. Gro«, H. Duda, A.W. Pacyna, J. Krok--Kowalski, Acta Phys. Pol. A 116, 964 (2009).[4] E. Malicka, T. Gro«, A. lebarski, A.W. Pacyna,J. Goraus, M. Fijaªkowski, J. Heimann, J. Phys.Chem. Solids 72, 974 (2011).[5] E. Malicka, T. Gro«, A.W. Pacyna, A. G¡gor,T. Mydlarz, J. Phys. Conf. Series 303, 012077(2011).[6] E. Malicka, T. Gro«, A. lebarski, A. G¡gor,A.W. Pacyna, R. Sitko, J. Goraus, T. Mydlarz,J. Heimann, Mater. Phys. Chem. 131, 142 (2011).[7] T. Gro«, A.W. Pacyna, E. Malicka, Solid State Phe-nom. 170, 213 (2011).[8] T. Gro«, J. Kopyczok, I. Oko«ska-Kozªowska, J. War-czewski, J. Magn. Magn. Mater. 111, 53 (1992).[9] R.M. White, Quantum Theory of Magnetism,McGraw-Hill, Inc., New York 1970.

Specific heat and magnetic properties of single-crystalline (Zn0.925In0.054)[Cr1.84In0.152]Se-4 semiconductor

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Specific heat and magnetic properties of single-crystalline (Zn0.925In0.054)[Cr1.84In0.152]Se-4 semiconductor

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