Orbital Contributions to the Transferred Hyperfine Fields in Rare-Earth Compounds

Abstract

Magnetic hyperfine fields acting on the nuclei of diamagnetic atoms in rare-earth intermetallic compounds are generally assumed to follow a form ${H}_{\mathrm{hf}}={H}_{s}({g}_{J}\ensuremath{-}1) 〈{J}_{\mathrm{z}}〉$. However, such an expression is inadequate to describe the detailed dependence of the transferred hyperfine fields as the rare-earth ion is changed. It is shown that an expression based on a Hamiltonian which includes orbital contributions to the hyperfine field can describe the available data on several series of rare-earth compounds. This dependence has the form ${H}_{\mathrm{hf}}=[({g}_{J}\ensuremath{-}1){H}_{01}+(2\ensuremath{-}{g}_{J}){H}_{10}+{c}_{n}{H}_{21}] 〈{J}_{z}〉$, where the ${c}_{n}$ are appropriate rare-earth reduced matrix elements. By fitting the extant data to this expression, we find that the orbital contributions ${H}_{10}$ and ${H}_{21}$ are appreciable. The general form of this expression is found to be valid for a variety of mechanisms which produce transferred and supertransferred hyperfine fields.