Magnetic properties of the spinel-type image

The spinel sulphide CuCr2S4CuCr2S4 is a metallic ferromagnet with a Curie temperature View the MathML sourceTc≃380K, while CuHf2S4CuHf2S4 has no magnetic anomaly. Magnetic properties of the quaternary spinel-type Cu(Cr1-xHfx)2S4Cu(Cr1-xHfx)2S4 system have been studied. With increasing xx the ferromagnetic properties are weakened gradually from a predominant ferromagnetic, a spin-glass, finally to a simple paramagnetic behavior. For the composition of x≃0.50x≃0.50, a re-entrant spin-glass phase could emerge, even though the Curie temperature is ill-defined as a ferromagnetic phase boundary. Specimens with x≥0.90x≥0.90 remain paramagnetic down to 4.2 K. A spin crossover phenomenon is found around 160 K in the specimens of x=0.50–0.70x=0.50–0.70. A step-like anomaly is manifestly detected in the magnetization, which corresponds with the change of the spin state. This crossover indicates that the spin state converts from high temperature S=2S=2 into low temperature View the MathML sourceS=32 states. In the ordered states in View the MathML sourceT<160K, the magnetic moment originates from only Cr3+Cr3+ ions.