Magnetic properties of compounds and solid solutions of rare-earth metals

Abstract

Studies of compounds and solid solutions of rare-earth elements (R) have already unearthed some generalizations regarding the behavior of this series of elements. In compounds with elements of the iron group (X) there is usually antiferromagnetic coupling between R and X when R is heavier than Gd, ferromagnetic coupling when R is lighter than Gd. This has been interpreted as interaction between spins only. The varying Curie temperatures of compounds of Eu and Gd with S, Se, and Te, especially in their solid solutions with each other, agree qualitatively with the theory of exchange through conduction electrons. In solid solutions R-R, when both R's are heavier than Gd, the Néel points (TN, transition temperature from spiral to paramagnetic phase), are proportional to Ḡ2/3, where Ḡ is the average of the deGennes factors (g-1)2J(J+1) of the R's. The Curie points of these solid solutions, however, are distinctly characteristic of the elements and seem to be closely related to their Stevens factors, the principal one of which changes from + to - in the middle of the heavy rare-earth series, between Ho and Er. Results for HoEr, DyEr, and DyEr3 crystals are interpreted in terms of the Kitano-Nagamiya theory of the mechanism of magnetization of the rare earths. Crystal anisotropy constants are derived for HoEr. Published and unpublished magnetic data illustrating these and other points will be shown and discussed. © 1967 The American Institute of Physics.