Magnetic susceptibility of diluted magnetic semiconductor alloys ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Co}}_{\mathit{x}}$S in the temperature range 40 mK≤T≤400 K

The magnetic susceptibility of ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Co}}_{\mathit{x}}$S has been measured over the temperature range 40 mK≤T≤400 K for alloy compositions 0.0016≤x≤0.082. The value of the effective exchange integral was obtained from the susceptibility data using the pair-correlation approximation and the mean-field approach, yielding ${\mathit{J}}_{\mathrm{eff}}$/${\mathit{k}}_{\mathit{B}}$=-22±4 K and -20±4 K, respectively. The dependence of χ on T indicates the presence of a small temperature-independent contribution, which has been found to be consistent with the prediction of the crystal-field model for a ${\mathrm{Co}}^{2+}$ ion in a wurtzite-structure lattice. Results of the crystal-field model, together with the pair-correlation approximation, were also successfully applied to describe the susceptibility anisotropy observed at very low temperatures.