THE COMPLEX STRUCTURE OF FE2-YSY MIXED-CRYSTALS((3D(6)) MAGNETISM IN HGSE1)

High magnetic field magnetization measurements of Hg1-xFexSe1-ySy(x = 0.002, y = 0.17; y = 0.28) at temperatures ranging from 1.6 to 119 K a nd in magnetic fields up to 20 T are reported. The magnetization of th e Fe2+ (3d(6)) ion in the investigated mixed anion crystals is shown t o be different from the Van Vleck behaviour. A theoretical description of the experimental data is based on an assumption that the electroni c structure (and thus magnetic properties) of the Fe2+(3d(6)) ion in a mixed anion crystal depends on its local environment. In this model t he total magnetization is calculated as a statistically weighted sum o f magnetizations found for specific local configurations. The model pr ovides a good quantitative description of the experimental data.