Magnetoelastic effects of iron-group ions in exchange fields

Abstract

Magnetoelastic properties of magnetic oxides can be enhanced by select 3d n transition ions. Spin-orbit coupling can survive in a cubic crystal field where a ground-state orbital triplet degeneracy is split by an axial deformation of the ligands. If the distortion stabilizes a singlet by a Jahn-Teller effect, there is reduced orbital angular momentum, and magnetoelastic effects are less significant; if the doublet is stabilized by a distortion of opposite sign the spin-orbit effect dominates, and the result is a strongly magnetoelastic ion. An analytical solution for the threshold of ligand distortion reversal confirms: (i) that the doublet cannot be stabilized without an exchange field, and (ii) that the smallest allowable ratio of spin-orbit coupling constant to the spontaneous distortion splitting is 2/3, which is reached only in the limit of an infinite exchange field. © 2002 American Institute of Physics.