Nonlinear microwave-magnetic resonator operated as a bistable device

The excitation of large amplitude spin waves causes a shift in the resonanc e frequency of a ferrite resonator towards higher frequency values. Using t his shift, a resonator can be designed to operate in a bistable mode where the history of the input power determines the output power. A theoretical c alculation for a resonator with a linewidth of 1.5 MHz, measured at 10 GHz, predicts a discontinuous jump in output power by a factor of about 3.5 as the input power is increased to about 0.7 mW. The phenomenological model th at describes the bistability also provides an explanation for the foldover of ferromagnetic resonance curves at high input power levels. An appropriat e choice for the operating frequency ensures that the estimated input power required to observe the bistable behavior is below the predicted threshold power for spin-wave auto-oscillations at the main resonance. (C) 1999 Amer ican Institute of Physics. [S0021-8979(99)35208-7].