Abstract
Highly pure single crystals of YIG are obtained by an FZ method and a remarkable photoinduced change of permeability is observed. Permeability is decreased over 90% by illumination of white light at 77 K and the influence remains up to about 260 K. By an annealing at 1100°C (oxygen atmosphere, 6 hours) in the sample preparation stage, the magnitude of the effect is reduced to 40%. After the sample is illuminated strongly at 77 K, the loss factor below 5 kHz shows double peaks, contrasting with the unilluminated flat curve on warming to 300 K. These activation energies are obtained as 0.3 and 0.1 eV. The mechanism of the effect is discussed in relation to relaxation processes with which these peaks are concerned, and F° center, an oxygen vacancy with two trapped electrons, is supposed to play an essential part.
