Magnetoelastic Interaction in EuIG

The magnetoelastic behavior of Eu³⁺ ion has been studied in the magnetic garnets by means of the stress‐induced shift in the FMR. At low temperatures the energy of the Eu³⁺ ion is determined by the exchange interaction which mixes excited J multiplets into the J=0 ground state. The anomalously large strength of the magnetoelastic interaction of Eu³⁺ may be understood in terms of a relatively simple model which involves strain‐induced variations in the anisotropic Eu³⁺−Fe³⁺ exchange coupling. The stress‐induced shifts in the FMR of EuIG may be attributed, mainly, to a change of order ${\mathrm{\chi H}}_{\mathrm{ex}}^2\mathrm{(\partial /\partial \epsilon )(}\ln H_{\mathrm{ex}})$ in the magnetic energy. The model successfully accounts for the variations in the magnetoelastic behavior for the mixed crystal system Eu_3−x Y_xFe_5−yGa_y0₁₂.