Paramagnetic anisotropy in high-T c 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.