Spin-wave experiments: Simultaneous pumping revisited

Abstract

Confirming theoretical predictions more than 30 years old, we show that the parametric instability threshold of microwave parallel-pumped spin waves in YIG spheres is reduced by the simultaneous application of an orthogonal RF field at half the pumping frequency. As a function of the orthogonal field, the reduction first increases with the square of the field, as predicted, and saturation is critically reached at the second-order Suhl instability threshold. In addition, we show that the auto-oscillation threshold is also affected by the orthogonal field, but not its amplitude nor its frequency.