DYNAMIC CONTROL OF INSTABILITY THRESHOLDS IN YTTRIUM-IRON-GARNET

Yttrium-iron-garnet (YIG) is an important material used in microwave l imiters and other devices. In this work, we use dual microwave (1-4 GH z) drives to study the behavior of magnetostatic and spin-wave modes i n YIG spheres and rectangular films. The samples are placed in a de ma gnetic field and driven by cw and pulse-modulated microwave excitation s at magnetostatic mode frequencies. A second microwave drive applied to the sample excites additional spin-wave modes that can interact wit h those arising from the original excitation and thereby affect the tr ansmission characteristics at the primary frequency. For both films an d spheres, we observe a significant decrease in transmission of the pr imary when the secondary frequency is tuned to approximately half that of the primary drive. This decrease is observed both in the steady st ate behavior and in the initial overshoot transient associated with pu lse modulation of the primary excitation. (C) 1997 American Institute of Physics.