Hyperfine Interactions in Rare-Earth Metals

Abstract

Estimates of the hyperfine interaction constants for the rare-earth metals are compiled from electron spin resonance and electron-nuclear double resonance data on salts, and atomic beam measurements on free atoms. Correction terms for second-order effects of the hyperfine structure are considered and shown generally to be small. Comparison with the experimental data (mostly from specific heat measurements below 1°K) shows close agreement in all cases except praseodymium, which is known not to have a co-operative phase. The temperature independent susceptibility of this metal below 4°K can be explained using a ferromagnetic exchange interaction of reasonable size, and the source of the observed hyperfine specific heat is discussed. In neodymium and samarium it is likely that crystal field effects are more important than exchange in determining the ground state in the co-operative phase.