Magnetic properties of gadolinium-rich alloys

The change in the saturated magnetic moment and the depression of $T_c$ caused by different nonmagnetic solutes in Gd suggest that the basic Ruderman-Kittel-Kasuya-Yosida theory for the $4f$—conduction-electron interaction is not directly applicable to alloys. The saturated moment, a local property, is found to vary linearly with the $\frac{c}{a}$ ratio. Remarkably, no correlation with $\frac{c}{a}$ is found for $T_C$, a global property; rather, $T_C$ is found to vary nearly linearly with the residual resistivity. It is shown that the $T_C$ dependence can be understood by taking into account the decreased $4f-4f$ coupling caused by the finite mean free path of the conduction electrons in the alloys.