Anisotropy of Fe3+ Ions in Yttrium Iron Garnet

Abstract

Using the single‐ion theory of anisotropy, it is possible to derive the anisotropy constants at 0°K for yttrium iron garnet in which the iron ions on tetrahedral and octahedral sites are replaced by nonmagnetic ions of gallium, indium, or scandium, respectively. The theoretical variation of K₁ has been compared with experimental values derived from torque measurements on single crystals of Y₃Ga_xFe_5−xO₁₂ (x=1.15), Y₃In_xFe_3−xO₁₂ (x=0.12, 0.20, 0.49), Y₃Sc_xFe_5−xO₁₂ (x=0.87) between 1.5° and 300°K. Although the results of the tetrahedral substitution fit the sample theory, the results for octahedral substitution give values of K₁ much lower than predicted. These values can be explained by assuming that the octahedral substitutions modify the crystal‐field parameters of the unsubstituted Fe³⁺ ions and thus alter their contribution to the over‐all magnetocrystalline anisotropy.