Spin-wave instability and ‘‘true’’ foldover in single-crystal YIG films (abstract)

Abstract

High-power pulsed microwave measurements of ferromagnetic resonance (FMR) in yttrium iron garnet (YIG) films have been extended to include all three in-plane and out-of-plane microwave and static field combinations for FMR. The 5.1-μm-thick films were prepared by liquid phase epitaxy on single-crystal gadolinium gallium garnet substrates and subsequently etched to form 500-μm circles. The FMR spectra were obtained with a 9.18-GHz pulse spectrometer as described in Ref. 1. The results confirm the conclusion of Ref. 1. The pulsed microwave FMR at high-power levels yields line broadening due to spin-wave instability processes, rather than the shifts and distorted profiles which occur due to heating under cw excitation conditions. The key new result is the explicit correlation between the microwave field amplitude for the onset of the line broadening and the FMR pump configuration. In addition to these line broadening effects at high power, a ‘‘true’’ foldover effect is observed for the perpendicular-to-plane static field case: the FMR shoulder shifts down in field at high powers, due to the nonlinear response and the limitations on that response from the spin wave instability processes.