Theory of Magnetostriction and g Factor in Ferrites

Abstract

A quantum mechanical theory based upon the Heitler‐London approximation has been developed to explain the spatial variation of magnetostriction and g factor in ferrites. As a first step, the electronic wave functions of cations of transition elements in the crystal field were found, taking into account the crystal structure of ferrites. The g factors of various cations in ferrites were determined by a method similar to that of Abragam and Pryce, and g factors thus found were related to those of ferrimagnetic resonance absorption by the use of the theory of Wangsness and the author. The magnetostriction was obtained by the perturbation method and it was concluded that there are four mechanisms predominant among those giving rise to magnetostriction. They are (1) the interplay of spin‐orbit interaction with the strain potential, (2) classical dipolar interaction, (3) the interplay of anisotropic exchange interaction with the strain potential, and (4) the interplay of the potential with the intra‐spin‐spin interaction. Other mechanisms were estimated to be ineffective. The predominant mechanisms in Ni ferrite are (1) and (2); in Co ferrite, (1); in magnetite, (1), (2), and (4). In annealed Mn ferrite and Cu ferrite, the mechanism (2) is most effective. In quenched Cu ferrite, both mechanisms (2) and (3) are the most important.