Annealing behavior and temperature dependence of the growth-induced magnetic anisotropy in epitaxial Sm-YIGG

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Abstract
The annealing behavior and temperature dependence of the growth‐induced magnetic anisotropy in epitaxial films of Y2.6Sm0.4Ga1.2Fe3.8O12 have been investigated. This garnet composition is presently being widely used for magnetic bubble domain device work. Decay times for the anisotropy are tens of hours at 1250°C and several hours at 1325°C. This rapid decrease in annealing time with increasing annealing temperature can be understood by postulating that oxygen vacancies play a significant role in determining the diffusion rate and that the oxygen vacancy concentration increases rapidly with increasing temperature. From these considerations, a lower limit of 2.8×107 yr is estimated for the decay time of the anisotropy at 100°C, based on an assumed activation energy of 1 eV. By using torque magnetometer measurements, the anisotropy has been found to vary by about an order of magnitude over the temperature range −10 to 110°C. Only two different kinds of temperature dependences were observed among films grown on four differently oriented substrates, in agreement with predictions of the site‐preference model for growth‐induced anisotropy. Also described is a new torque magnetometer technique for measuring the effective anisotropy field in magnetic materials which support bubble domains.