Phase relationships and magnetic phase diagram in the system Mn1−xCuxCr2S4

Ternary spinel compounds have been found in the system Mn_1?xCu_xCr₂S₄ for x < 0.4 and x ? 0.8. The unit cell parameter does not follow a Vegard law. Magnetization measurements up to 150 kOe for Mn_0.95Cu_0.05Cr₂S₄ show three magnetic structures: Néel ferrimagnet, Yafet-Kittel and tridimensional. The magnetic phase diagram has been calculated within the molecular field approximation. There is strong evidence for the non-existence of Mn³⁺. Our findings are in conformity with a model proposed by Goodenough.