Photo-induced low-frequency magnetic permeability of an iron-yttrium garnet doped with silicon

The photomagnetic properties of an iron-yttrium garnet, viz. the photo-induced change in the magnetic permeability and the parameters of the magnetic hysteresis loop, are strongly dependent on the amplitude of the low-frequency remagnetizing field (Hsub(m)) with which the photosensitive characteristic is measured. At low values of Hsub(m) the magnetic permeability at 77 K during irradiation with light experiences a giant Barkhausen jump. The photoinduced jump involves an unstable equilibrium of the domain structure. A state characterized by a constant magnetic permeability and a nonhysteresis remagnetization cycle is observed in the illuminated sample. A photoinduced increase of the total magnetic permeability μsub(π) is observed in the range of Hsub(m) high values. It is shown that higher order harmonics are responsible for the light-induced increase of μsub(π)