Spin wave instabilities in an axially magnetized YIG rod

Instabilities of spin waves in an axially magnetized YIG rod are studied in the volume magnetostatic and magnetoelastic regions using a spectrum analyzer. In the magnetoelastic region, the strength of the static magnetic field at which the resonance absorption occurs decreases with increasing input microwave power. When the input power reaches a threshold value, each absorption peak shows an abrupt jump and instabilities appear with oscillation frequencies of 300 kHz to 10 MHz. Instabilities may attribute to the second-order parametric process of the volume magnetostatic waves. In the magnetoelastic region, the intensities of the spectrum in lower sidebands are much larger than those in higher sidebands. However, in the volume magnetostatic region, the intensities of the spectrum in lower and higher sidebands have nearly equal amplitudes.