Photoinduced variation of magnetic complex permeabilities μ\u27 and μ" as a function of temperature or time is reviewed in yttrium iron garnet which has been studied in our laboratories. Our basic idea is; when the oxygen vacancies are made empty by photoexcitation, the resulting perturbation is larger than when this vacancy has one or two electrons. New data and the further discussion based on the localized and band model are also described
