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MAGNETIC SYSTEMS 2009High magnetic field study in chromium-based Mn 1−x Cd x Cr 2 S 4 thiospinelsMaterials with spinel AB 2 X 4 structure are widely studiedbecause of outstanding physical properties, e.g. halfmetallicityand colossal magnetoresistance. Among thesematerials, the MnCr 2 S 4 thiospinel presents a collinear ferrimagneticstructure at 65 K and a Yafet-Kittel transitionat ∼ 6 K toward a triangular non collinear state [Tsurkanet al., Phys. Rev. B 68, 134434 (2003)]. Application ofvery high magnetic fields produces a reorientation of themoments toward a ferromagnetic state.We investigate here a solid solution obtained by partial substitutionof magnetic Mn by non-magnetic Cd. Sampleswere prepared from high-purity elements, sealed in evacuatedquartz ampoules, using I 2 as transport agent. Ampouleswere slowly heated up to 800 ◦ C over a period of1 week. The resultant was reground, pelletized and firedat 900 ◦ C for 3 days. Samples were characterized by X-raydiffraction. Patterns were fully indexed in the Space GroupFd3m, with no secondary phases observed within the limitsof the experimental detection. Magnetic measurementswere performed on specimens cut from ceramic pellets.The ordered regime was investigated through ZFC/FC magnetizationcycles performed under low applied field (figure131). Samples were first cooled under non-magneticfield and then warmed from 2 up to 300 K under the appliedfield of 0.01 T (ZFC mode). Once in the paramagnetic state,samples were then cooled down to the lowest temperatureof 2 K under the same applied field (FC mode).into a stronger overall ferromagnetism [Barahona et al., J.Alloys Comp. 480, 291 (2009)].Figure 132: Magnetization at given temperatures for theMn 1−x Cd x Cr 2 S 4 solid solution.In order to obtain a better knowledge concerning spins reorientation,magnetization measurements were performedat fixed temperatures in fields up to 20 T (figure 132). Datashow a progressive loss of the antiferromagnetic interactionsbetween A and B sublattices, favouring the parallelalignment of moments pointing into the same direction, thatis, the ferromagnetism of the Cr 3+ network. To be noticedthat the threshold field for the moments realignmentis 5 times smaller (H C ∼ 6 − 8 T) than the one reported forpure MnCr 2 S 4 . However, for all samples, magnetizationsdo not attain full saturation of free spins at 20 T (see figure133).Figure 131: ZFC/FC magnetization for Mn 1−x Cd x Cr 2 S 4 solidsolution (ZFC : open symbols ; FC : filled symbols).In the parent compound MnCr 2 S 4 , the Cr 3+ and Mn 2+networks are ferromagnetic but point in opposite direction,creating a ferrimagnetic state, while in the solid solution(Mn 1−x Cd x )Cr 2 S 4 , the antiferromagnetic interactionbetween the Mn and Cr networks is progressively lost whenthe content of non-magnetic cadmium increases, resultingFigure 133: Normalized magnetization at 4 Kfor Mn 1−x Cd x Cr 2 S 4 . The normalization was done with respectto effective magnetic moment calculated from high temperaturedata of figure 131 fitted to Curie-Weiss law (not shown).A. B. AntunesP. Barahona (Instituto de Ciencias Básicas, Universidad Católica del Maule, Talca, Chile), A. Galdamez, V. Manriquez(Departamento de Química, Facultad de Ciencias, Universidad de Chile, Santiago, Chile), C. M. Campos, O. Peña(Sciences Chimiques de Rennes, Université de Rennes 1, Rennes, France)92