Elementary Excitations of High Degree Pair Interactions in Rare Earth Compounds

Abstract

Rare earth ions retain many of their free ion properties when they form solids. In particular, the total angular momentum \(\vec J = \vec L + \vec S\) remains a relatively good quantum number. In a first approximation the effect of the crystal field surrounding the rare earth ion is to split the (2J + 1)-fold degeneracy of the ground manifold. If the surrounding has high point group symmetry, e. g., cubic Oh symmetry, the split levels will still be degenerate; the orbital angular momentum of the rare earth ion is not quenched. Therefore we expect that the effects of orbital angular momentum on the magneto-thermal properties of rare earth compounds are quite marked.