Ferromagnetic resonance of single-crystal YIG/gadolinium gallium garnet/YIG layers

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Abstract
We report on the microwave properties of single-crystal YIG/gadolinium gallium garnet/YIG grown in (110) layers, where YIG is yttrium iron garnet. The YIG layers were sufficiently thin so that single domain ferromagnetic resonance (FMR) was observed. FMR fields were measured as a function of field direction and magnitude and frequency. Bulk magnetic parameters deduced from FMR and vibrating-sample magnetometer measurements agree with published values. In addition, FMR measurements at low fields show typical ‘‘butterfly’’ variations of the FMR fields with a frequency for H, the magnetic field, parallel to either the 〈100〉 or 〈110〉 axis. However, a new butterfly pattern was also observed for the magnetic field parallel to the 〈111〉 axis. This result is intrinsic to layered structures and not to single layer excitations. We attribute this new result to nonuniform distribution of strain in the two YIG layers, and as a consequence, we predict that magnetostatic fringe fields from edges are sufficient to induce spin-flop magnetic configurations in single-crystal YIG double layers.