Photocontrol of spin-glass state in Mg1.5FeTi0.5O4 spinel ferrite films

A spin-glass state up to 210 K has been found in (Mg, Fe){Mg,Fe,Ti}(2)O-4 s pinel ferrite thin films formed on alpha-Al2O3(0001) substrates. The films exhibit long-time relaxation of the magnetization in zero-field-cooled oper ation below 210 K; also, the ac susceptibility measurements show the presen ce of frequency-dependent cusp temperature. Both of the above observations are characteristic features of a spin glass. The change of magnetic state i n the films from a spin glass to ferrimagnet has been achieved over a wide temperature range below 160 K by means of light irradiation. (C) 2000 Ameri can Institute of Physics. [S0003-6951(00)04209-1].