Effect of cation substitution on magnetic properties in Mn _1-xA'_xCr₂S₄ (A' = Cd, Zn) thiospinel series

Colossal magnetoresistance (CMR) materials such as REMnO₃ perovskites and AB₂S₄ thiospinels have been well studied in the past. The authors present thiospinel compounds with A = Mn, since they may be viewed as a link to REMnO₃ CMR perovskites. Ferrimagnetic MnCr₂S₄ is known to present a T_c of 65 K and a magnetic transition towards a non-collinear Yafet-Kittel state. The (Mn _1-xA'_x)Cr₂S₄ series (A = Cd, Zn) was synthesised at 850°C. This series crystallises in the space group Fd3m with a close to 10 Å. When A' = Cd (T_c ranging from 68 K, x = 0·2, to 79 K, x = 0·6), the ferromagnetic features are enhanced, indicating that antiferromagnetism between Mn spins is progressively lost. For A' = Zn, two magnetic transitions take place, one at 15 K, which is reminiscent of the antiferromagnetic state of ZnCr₂S₄ and another one at T_c = 115 K. Impurities which could be responsible of these two magnetic states are excluded.