Paramagnetic anisotropy in high-<i>T</i> <i>c</i> superconductors

Abstract

Magnetic alignment of RBa2Cu3O7−x particles results from anisotropy in paramagnetic susceptibility, an anisotropy that differs in sign for different rare earths. Various factors contributing to this anisotropy are discussed, particularly the rare-earth single-ion anisotropy associated with crystal fields and second-order Stevens factors. For R=Eu, the observed anisotropy is consistent with that expected from the crystal-field splitting of J=1 excited levels.