PHOTOINDUCED IRREVERSIBLE EFFECTS ON MAGNETIC PROPERTIES AND ALLIED PHENOMENA IN MAGNETIC OXIDES X

This is a review which concerns with mainly the relaxation phenomena in permeability of magnetic oxides. In addition the study is, however, reported in our laboratory in 1997,which was in press. In single crystals of yttrium iron garnet irradiated with an intense visible light at 77K, a remarkable change of the temperature dependence of complex permeabilities μ' and μ" is observed. Simultaneously, conspicuous double peaks of photoinduced disaccommodation, DA around 130 K(DA(I)) and 200 K(DA(II)) were found, with correlative onset of the irreversible decrease of μ' at low temperature. Activation energies of these peaks are estimated 0.46eV for DA(I) and 0.7 eV for DA(II). In addition, we observed the third peak (DAIII, 0.88 eV), independent of irradiation around the room temperature. For an explanation of these results, a simple model is presented here for explaining these results. This review proposes also a new approach to studying the role of vacancy migration of YIG by the simple magnetic technique.