Garnet compositions for submicron bubbles with low damping constants

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Abstract
Thin single crystalline films of composition (BiYLu)3(FeGa)5O12 have been grown by liquid phase epitaxy on 〈111〉 substrates with zero lattice mismatch. Optimisation of the Bi:Y:Lu ratio has lead to a 1 μm bubble film on Gd3Ga5O12 (Q = 3.6, 4 πM = 600 gauss and FMRΔH at 10 GHz = 2.8 Oe) and a 0.8 μm bubble film on Sm3Ga5O12 (Q = 2.7, 4 πM = 930 gauss and ΔH = 4.3 Oe). The dynamic coercive fields for these films was <1 Oe. Smaller bubble diameters seem to be feasible in this system. From ferrimagnetic resonance linewidth measurements at 10 GHz it appears that the damping constants in these films are only two times as high as in pure YIG. To increase the damping small concentrations of Sm have been added. For 3 μm bubble films a study of the correlation between the damping constants calculated from the FMR linwidths and the damping constants calculated from the bubble mobilities measured by a translation technique has been made. The agreement between these constants in these films was excellent.