Effect of cation substitution on magnetic properties in Mn _1−x A’ _x Cr ₂ S ₄ (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 (Mn1−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.