Magnetic Behavior of Cobalt and of Nickel in Compounds with Rare Earth Metals

Abstract

We discuss the value of the intrinsic magnetic moment of cobalt in intermetallic compounds of the formula R_xCo_v, where R is a rare earth element or yttrium. The experimental values of this moment are determined from the results of neutron‐diffraction studies and those of measurements of the absolute saturation magnetization on certain compounds: R₂Co₁₇, RCo₅, R₂Co₇, RCo₃, and RCo₂. The electronic configuration of cobalt is greatly modified, both by the addition of the conduction electrons of the rare earth atoms or yttrium and by the magnetic interactions resulting from these atoms. This behavior of cobalt permits the explanation of certain apparent anomalies in the properties of the alloys, viz., the differences between the Curie temperatures of the compounds of the same series are too large to be attributable to the interactions between the rare earths along; the magnetizations and Curie temperatures of the alloys with cerium are smaller than those of the corresponding compounds with yttrium; and certain compounds RCo₂ present a ferrimagnetic‐paramagnetic first‐order transition. The variation of the Curie temperatures of the compounds R_xNi_v, as a function of rare earth percentage, can be explained by the behavior of the moment of nickel analogous to that of cobalt.