The magnetostriction of rare-earth garnets containing gallium and europium: Old theory for new problems

A calculation is made of the effect of gallium substitution upon the magnetostriction of rare-earth garnets, a problem of some interest because of the use of gallium substituted garnets as bubble-domain materials. The gallium alters the contribution to magnetostriction of the iron lattices by simple dilution and of the rare-earth lattice by reducing the exchange field acting upon the rare-earth ions. Site preference considerations must be included in the calculation. Expressions are produced for predicting the effect upon the magnetostriction constants of gallium substitution into a typical rare-earth garnet. The special case of EuIG is treated separately. Since the contribution to magnetostriction of the Eu³⁺ions depends on the square of the exchange field, EuIG is more strongly affected by Ga substitution than most garnets.