Magnetostatic wave dynamic magnetization response in yttrium iron garnet films

Abstract

The dynamic microwave magnetization (DMM) amplitude of magnetostatic waves in yttrium iron garnet films at 5–6 GHz has been measured as a function of input power. The measurement is based on the characteristic frequency shift in the power transmission spectrum. This shift is related to the reduction of the effective static magnetization and, therefore, the increase of the DMM amplitude at high power. The measurements were made on 7.2-μm-thick, single-crystal yttrium iron garnet films. A pulsed frequency-swept microwave signal at 5–6 GHz was used to launch the magnetostatic waves. The signals were excited and detected by planar microstrip transducers. Measurements were made for magnetostatic forward volume waves (MSFVW) and magnetostatic surface waves (MSSW). The duty cycle of the pulsed microwave signal was kept at 0.1% in order to avoid sample heating effects. The shifts for small features in the transmission vs frequency profiles were used to determine the DMM amplitudes. At low power, the DMM amplitude increased with power. Saturation occurred at high power. The results indicate a saturation DMM response at about 10% of the saturation magnetization for input power in the 3–4 W range for MSFVW signals and above 0.5 W for MSSW signals.