Magnetization of Compounds of Rare Earths with Platinum Metals

Measurements have been made of the Curie points and magnetic moments of three series of compounds (Laves phases) $M{\mathrm{Ir}}_2$, $M{\mathrm{Os}}_2$, and $M{\mathrm{Ru}}_2$, where $M$ is a rare-earth element. The Curie point is highest (85°K) for the compounds containing Gd and falls away when the rare earths have larger or smaller atomic numbers. This dependence of Curie point on the rare-earth element is in accord with the idea that the principal exchange interaction is between the spins of the $4f$ shell of the rare-earth ions and the conduction electrons. The magnetic moments are closely related to, but differ somewhat from, the values of $\mathrm{Jg}$ for the trivalent ions of $M$.