TEMPERATURE DEPENDENCE OF GROWTH-INDUCED MAGNETIC ANISO-TROPY IN EPITAXIAL GARNET FILMS BY RESONANCE TECHNIQUES

Abstract

Using ferromagnetic resonance techniques, we have measured the growth‐induced uniaxial magnetic anisotropy, Ku, vs. T, of epitaxial garnet films of composition Er2EuGa0.7A10.7Fe3.6012 from 98°K to the Curie point, 370°K. The films were grown by liquid phase epitaxy on {111} substrates of Gd3Ga5012. At 300°K they supported bubbles ∼5μm in diameter with mobilities of ∼320 cm/sec Oe. An unusual combination of properties of these films, i.e., the reasonably narrow resonance line widths, the large g‐factors (∼5), the suitable values of Ku and K1, and the uniaxiality arising from the {111} substrate orientation made observation of both the transverse and longitudinal resonances possible at 17.5 GHz over this entire temperature range, and thus enabled quantitative measurements of Ku(T) to be obtained for the first time. Ku was found to vary as (Tc−T)1.15 from 98°K to 350°K. At 300°K, Ku is 1.33×104 erg/cm3. Attempts can now be made to correlate quantitatively Ku(T) with theoretical studies. The temperature dependence of 2Ku/M, 4πM, g‐factor, and K1 (including small strain terms) have also been measured. An interesting new feature of the uniaxial field, 2Ku/M, is a reversal in slope with a maximum at 185°K. This indicates that below 185°K, M increases faster than Ku. This does not occur at any T⪞20°K for the cubic term, K1/M, of any known mixed or single rare earth iron garnet.