Thermal Change of Complex Permeability in Photoexcited Yttrium Iron Garnet

A photoinduced decrease in the initial magnetic permeability below 20 kHz was observed at 77K in yttrium iron garnet (YIG) single crystal with a small amount of Ga (0.0625) and some oxygen deficiency. On warming a sample which had previously been illuminated with white light, the complex permeability was found to show photoinduced dis-accommodation and triple peaks of the imaginary part of the permeability ¿" as a function of temperature. Furthermore, it was observed that each ¿" peak depended on the illumination time. These features are discussed and interpreted on the basis of a modified "two center" model.