An investigation of the zero-field splitting of Fe³⁺ions at the tetragonal FeF₅O site in Fe³⁺:KMgF₃crystals

Abstract

The extremely large zero-field splitting of Fe3+ ions at the tetragonal FeF5O site in Fe3+:KMgF3 crystals has been interpreted on the basis of a second- to sixth-order perturbation approach, in which the spin-orbit coupling is regarded as the perturbation to the crystal-field and electrostatic interactions. The replacement of O2- for F- and its induced lattice relaxation are shown to give rise to a strong tetragonal crystal field which in turn results in the large zero-field splitting. Of the various sources contributing to the zero-field splitting, the displacements of the O2- and F- ions are found to be important.