Ferromagnetic resonance as a tool for evaluating YIG type materials

Ferromagnetic resonance techniques have been used to evaluate the magnetic parameters in thin films of YIG type materials. YIG disk films having thickness from 0.39 μm to 1.15 μm and diameters from 250 μm to 1000 μm and grown by CVD on GGG substrates where investigated from 1.fK to 300 K and at 10 GHz and 25 GHz. The magnetization, obtained from parallel and perpendicular resonance data, is in agreement with bulk values in the temperature range 300 K to 80 K. Below 80 K the magnetization deviates dramatically from bulk values and by 4 K the magnetization is decreasing by 30 Oe/K. The linewidth at 10 GHz is observed to be about 0.40 Oe from 300 K to 200 K then increases to a maximum of 2.00 Oe at 50 K. At 2 K the linewidth has decreased to about 0.50 Oe. The g value, being 2.006 at 300 K follows bulk values to 80 K. Below 80 K the g value increases dramatically, reaching 2.02 by 20 K. The in-plane anisotropy, cubic term, was measured and found to be in agreement with bulk values at all temperatures. A spinwave exchange constant of 3.4 × 10^-12cm²was observed at room temperature for films having pinned surface spins. This value has decreased by about 15 percent at 80 K and remains nearly constant from 80 K to 20 K. From analysis of the magnetoexchange modes, a repulsion between magnetoexchange branches was observed for films having pinned surface spins and no repulsion for unpinned surface spins. An exchange dominated surface mode has also been observed.