Konstantin P. Belov

Phase transition from spin glass to long-range magnetic order in semiconductor spinels CuCr1.5+0.5xSb0.5−0.5xS4 (x=0.34 and 0.4)

Reentrant behavior to a spin glass state is discovered in the solid solution system CuCr1.5+0.5xSbx0.5−0.5xS4 with x=0.34 and 0.4. The spin-glass transition temperature Tf determined from the kink in the temperature dependence of the initial susceptibility in an alternating magnetic field depends on the measurement frequency ω. It is shown that the frequency dependence Tf(ω) is a power-law function 1/ω=(1/ω0)[Tf/(Tf− T*)]zv with zv=7.7 for both compositions. For the composition with x=0.34 a maximum is observed near T* in the temperature dependence of the resistivity. These facts indicate that the transition from the spin glass to long-range magnetic order is a phase transition.

Magnetic Properties of CdCr2Se4

The dependence of magnetization, δ, and resistivity, ρ, on temperature T and magnetic field H has been studies near Curie point and at somewhat higher temperatures for single crystals of CdCr2Se4 deficient in selenium or doped with indium or copper. The magnetic field has a pronounced effect on the Tc values determined by extrapolation of the steepest section of the δ (T)‐ curves to the temperature axis. Thus, an increase of the field strength from 0.9 to 12.7 kOe leads to a 20 to 30° high temperature shift of the Curie point. The δ (H) curves measured near Tc are characterized by critical field values in the vicinity of which magnetization increases stepwise by about 80%. Copper doped crystals exhibit thermomagnetic hysteresis and those containing indium show positive magnetic resistivity in the temperature region where the critical field phenomena are observed. The experimental data are explained by the formation of ferrons, that is ferromagnetic microregions, under the action of magnetic field. The f e...