Linear and nonlinear spin wave resonances in a very thin amorphous wire

Linear and nonlinear FMR spectra of a very thin amorphous wire are investigated. A phenomena called “spin wave ripple” is reported here. It is observed on the low field side of the linear resonance curve and is attributed to the excitation of radial standing spin waves with the energy corresponding to the incident microwave frequency. The fine structure of the nonlinear resonance curves, recently observed on thin amorphous wires, is then explained by the dipole-exchange models of a cylinder parametrically excited by Suhl's first-order process. This explanation is consistent with the value of the exchange stiffness constant A determined from the spin wave ripple.