Model calculation of the superexchange interaction in rare earth iron garnets

The superexchange interactions between rare ions and ions in rare earth iron garnets investigated theoretically an overlap model of the interaction. For YbIG, it is shown that the dominant component of the isotropic exchange field arises from the ferric ions on nearest neighbour tetrahedrally coordinated (d) sites. The magnitude of the interaction is calculated to be 49 cm(-1). Both results well with experiment. Exchange via the rare earth 5p shell is shown to produce the dominant term the isotropic component of the interaction.