Ferromagnetic resonance of single-crystal YIG/GGG/YIG layers (abstract)

Abstract

We report on the microwave properties of single crystal of YIG/GGG/YIG grown in (11̄0) layers. 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, magnitude, and frequency. Bulk magnetic parameters were deduced from FMR and VSM measurements. For the YIG layer next to the GGG substrate, we measured 4πM(1)eff =1750 G, 2K(1)l/M =−82 Oe, K(1)u =0, and for the other layer 4πM(2)eff =1256 G, 2K(2)1/M=−82 Oe, 2K(2)u/M =50 Oe, g=2.025, where 4πM(i)eff (i=1,2) is the sum of the saturation magnetization and uniaxial magnetic anisotropy field normal to the film plane, and K(i)l and K(i)u (i=1,2) are cubic and in-plane uniaxial anistropy energies, respectively. FMR measurements at low fields show typical ‘‘butterfly’’ variations1 of FMR fields versus frequency for H, the magnetic field parallel to either 〈110〉 or 〈100〉 axis. However, a new butterfly pattern was also observed for the magnetic field parallel to the 〈111〉 axis. This new result is intrinsic to layered structure and not to single-layer excitations. We explain this data in terms of nonuniform distribution of strain in the two YIG layers and misalignment between the magnetization direction in the two YIG layers in zero field. For a reverse field of −2 Oe the misalignment is total and equal to 180°