Spin-glass-like behaviour and magnetic order in Mn[Cr0.5Ga1.5]S4 spinels

Magnetization and susceptibility were investigated as a function of temperature and magnetic field in polycrystalline Mn[Cr0.5Ga1.5]S4 spinel. The dc susceptibility measurements at 919 Oe showed a disordered ferrimagnetic behaviour with a Curie–Weiss temperature θCW=−55 K and an effective magnetic moment of 5.96 μB close to the spin-only value of 6.52 μB for Cr3+ and Mn2+ ions in the 3d3 and 3d5 configurations, respectively. The magnetization measured at 100 Oe revealed the multiple magnetic transitions with a sharp maximum at the Néel temperature TN=3.9 K, a minimum at the Yafet-Kittel temperature TYK=5 K, a broad maximum at the freezing temperature Tf=7.9 K, and an inflection point at the Curie temperature TC=48 K indicating a transition to paramagnetic phase. A large splitting between the zero-field-cooled (ZFC) and field-cooled (FC) magnetizations at a temperature smaller than TC suggests the presence of spin-glass-like behaviour. This behaviour is considered in a framework of competing interactions between the antiferromagnetic ordering of the A(Mn) sublattice and the ferromagnetic ordering of the B(Cr) sublattice.