Examination of magnetostatic waves by new optical and induction probes

Abstract

New optical and induction probes have been developed and used to investigate microwave (1–4 GHz) magnetostatic waves (MSW) propagating in yttrium iron garnet (YIG) thin films (5–50 μm). The optical probe uses the magnetooptic properties of YIG, and light from a 45 mW, 1.15 μm HeNe laser, to examine rfmagnetization of MSW. Focused light for localized probing has achieved a spatial resolution of 100 μm. The induction probe senses the rf magnetic field, which fringes from the surface of YIG thin films, with metal loops of either gold wire wrapped around a plastic support or aluminum photolithographically fabricated on glass. The highest spatial resolution was attained with 45μm aluminum loops. The optical probe has been used to examine the amplitude of linear and nonlinear forward volume waves (MSFVW). Nonlinear effects are characterized by MSFVW saturation and then a decline as input power to the wave increased. Localized probing of nonlinear properties showed, that over small regions, a monotonic increase of light modulation with increasing microwave input power to MSFVW does not always occur. MSFVW in the linear regime were studied for evolution of the amplitude profile as it propagated from the launching antenna. Magnetostatic surface (MSSW) and backward volume (MSBVW) waves have been explored with the induction probe for amplitude and dispersion relation. In a uniform bias field, an apparent form of spatial focusing was exhibited by MSSW. Direct measure of wavelengths of MSSW and MSBVW gave the dispersion relations.