Magnetic properties ofCeSb1−xTexsolid solutions

Abstract

We report magnetic properties of $\mathrm{Ce}{\mathrm{Sb}}_{1\ensuremath{-}x}{\mathrm{Te}}_{x}$ solid solutions in the whole range of composition $0lxl1$. We find that a simple Heisenberg interaction treated in the molecular-field approximation is sufficient to describe the experimental results at $xg0.05$. In particular, a linear $x$ dependence of the effective exchange-coupling constants ${\overline{\ensuremath{\Gamma}}}_{1}$ and ${\overline{\ensuremath{\Gamma}}}_{2}$ between nearest and next-nearest neighbors, respectively, accounts for the nonlinear behavior of the variations of the N\'eel temperature ${T}_{N}(x)$ which goes through a minimum at $x\ensuremath{\simeq}0.07$. This model, however, is too crude to account for the magnetic properties at concentrations $xl0.05$, such as a maximum of the crystal-field splitting energy $\ensuremath{\Delta}(x)$ between the ${\ensuremath{\Gamma}}_{7}$ and ${\ensuremath{\Gamma}}_{8}$ levels of the $4f$-electron states at $x\ensuremath{\simeq}0.04$, a maximum of the paramagnetic Curie temperature ${\ensuremath{\Theta}}^{*}(x)$ at $x\ensuremath{\simeq}0.02$, and a very strong monotonic decrease of ${T}_{N}(x)$ in the whole range $0lxl0.05$. To account for these experimental data, we have studied the fourth-order indirect exchange in the mixing parameter, derived after a canonical transformation of the Schrieffer-Wolff type is applied to the multisite Anderson model when both the crystal-field effects and the large spin-orbit coupling of the intermediate state of the Ce electron in the $4f$ subshell are taken into account. This model provides an overall understanding of the magnetic properties of $\mathrm{Ce}{\mathrm{Sb}}_{1\ensuremath{-}x}{\mathrm{Te}}_{x}$ solutions at all $x$. A detailed discussion of this model with respect to previous models is also reported.