The nature of spin-glass phase in semiconducting spin glasses of the $x$CuCr$_2$Se$_4$-$(1-x)$Cu$_{0,5}$Me$_{0,5}$Cr$_2$Se$_4$ (Me${}={}$In, Ga) system

The dependence of magnetoresistance $\Delta\rho/\rho$ on the square of magnetization $\sigma^2$ in strong magnetic fields has be studied for the $x$CuCr$_2$Se$_4$-$(1-x)$Cu$_{0,5}$Me$_{0,5}$Cr$_2$Se$_4$ (Me${}={}$In, Ga) system. Both in spin glasses and in the reciprocal spin glass, the slope of the $(\Delta\rho/\rho)(\sigma^2)$ dependences was shown to change at freezing temperature $T_f$ suggesting that at $T=T_f$, the spin system experienced substantial rearrangement, that is, underwent a thermodynamic phase transition. The spin-glass phase in the reciprocal spin glass was shown to consist of spins of separate Cr$^{3+}$ ions, whereas spin glasses contained not only these ions but also interacting ferromagnetic clusters.