In single crystals of yttrium iron garnet irradiated with laser (the most effective wavelength is 700nm) or white light at 77K, a remarkable change of the temperature dependence of complex permeabilities μ′ and μ″ is observed, which is peculiar to photoinduced magnetic effect. Simultaneously, conspicuous double peaks of DA around 125K and 200K below room temperature were found to be induced by light-irradiation, with correlative onset of the irreversible decrease of permeability insensitive to demagnetization at low temperature. The height of potential barrier around oxygen vacancy may be estimated 0.3eV. In order to explain these observations, we propose that oxygen defects provide a mechanism for occurrence of photomagnetic effects and discuss its validity; the review of these area of our laboratory in 1996 is given
