Photocontrol of spin-glass state in spinel and garnet ferrite thin films

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Spin-glass states and its photo-control have been investigated in epitaxial spinel and garnet ferrite thin films prepared by pulsed-laser deposition (PLD) technique. The films were found to display the spin-glass behaviors with spin-freezing temperature Tf near room temperature. The zero-field-cooled (ZFC) magnetization increases following light irradiation below Tf, indicating the melt of spin-glass. In (Ni, Zn, Fe, Ti)3O4 spinel-type films, this photo-induced magnetization (PIM) was found to increase with increasing Ti content. An analysis of the excitation energy dependence and the compositional dependence of the PIM revealed that the photo-induced charge-transfer between Ti and Fe ions, which results in a change in local magnetic anisotropy, is responsible for PIM. In Y3(Al, Fe, Si)5O12 garnet-type ferrite films, the spin-glass with high Tf (~390K) was observed and the room temperature PIM was detected through the giant magneto-optical (MO) effects. These garnet ferrite films can be utilized in the development of the ultrafast photon-mode MO memories which will replace the conventional thermo-driven memories.