The power dependence of auto-oscillations due to modulation instability in perpendicularly magnetized YIG films

Auto-oscillations (AO) were studied in a small YIG film magnetized normally to its surface. We measured those AO that appear at fields beyond the (1,1) forward volume magnetostatic line, where new power-sensitive peaks were observed recently. The threshold power of these AO is very low. Three types of AO were noticed: (a) AO whose frequency increases with the pumping power; (b) AO whose frequency decreases with increasing the pumping power; (c) A broad AO band at zero frequency whose width and intensity increase with the pumping power. It seems that current AO theories do not explain the nature of AO of types (b) and (c).