EPR of Fe3+pairs in α-Al2O3

Abstract
EPR spectra of exchange coupled pairs of Fe3+ ions in alpha -Al2O3 are reported. An analysis of two pairs which C3 symmetry shows that the magnitudes of the isotropic exchange parameters are small, as in pure haematite, but that the sign of this interaction is opposite to that in the magnetically concentrated material for both pairs. The nearest neighbours are antiferromagnetic, J=1.4 (0.3) cm-1; the next nearest neighbours are ferromagnetic J=-2.3 (0.7) cm-1. Biquadratic exchange is small for both these pairs. Parameters of the spin Hamiltonian for most of the total spin levels of each pair have been determined. A new method has been developed which allows transitions from different pairs of the same symmetry to be distinguished.

This publication has 22 references indexed in Scilit: