Spin Crossover in Cu$\text{}_{x}$Co$\text{}_{y}$Cr$\text{}_{z}$Se$\text{}_{4}$ Semiconductors

Magnetization and magnetic susceptibility measured in the zero-field-cooled mode were used to study the spin crossover transition in polycrystalline Cu$\text{}_{x}$Co$\text{}_{y}$Cr$\text{}_{z}$Se$\text{}_{4}$ compounds. With increasing Co content a transition from ferromagnetic order via ferrimagnetic one to antiferromagnetic-like behaviour was observed. This transition is accompanied with a lowering symmetry from cubic to monoclinic and for the latter the spin crossover phenomenon occurs. These results are considered in a framework of the ligand-field split and the spin-orbit coupling.