Microwave-Induced DC Response of Spin Wave Resonance Driven by an Anisotropic Built-In Field in a Permalloy Thin Strip

The microwave-induced dc response has been investigated in an in-plane magnetized permalloy strip. The spin wave resonances (SWRs) are observed. The SWR signals get anomalously suppressed when the direction of the specimen or the amplitude of the microwave frequencies is changed. Such suppression occurs at frequencies of less than 11 GHz, while the resonant field is as weak as less than 200 Oe. They are finally quantitatively interpreted by introducing an anisotropic built-in magnetic field that describes the shape anisotropy of the specimen.