Light-induced uniaxial magnetic anisotropy characterized by amplitude, times of creation ${\tau }_1,$ and a vanishing ${\tau }_2$ was studied. The investigation was performed on YIG (yttrium iron garnet):Co,Ca,Ge liquid-phase epitaxy films using a very sensitive method—observation of changes of magnetic domain structure with a different in-plane magnetization component induced by linearly polarized light pulses. An argon laser $(\lambda =488\mathrm{}$ nm) was used. The effective field $H_L$ was introduced to describe the photoinduced uniaxial magnetic-anisotropy amplitude. These domain changes were studied within the temperature range of 160–300 K. With an increase in temperature an increase in ${\tau }_1,$ a decrease in ${\tau }_2,$ and a drastic decrease in $H_L$ were found. The appearance of the photoinduced anisotropy is explained by light-induced rearrangement of strongly anisotropic ${\mathrm{Co}}^{2+}$ octahedral ions. A microscopic model was proposed where ion rearrangement is connected with electron excitations into the conducting band. Both thermal and light-induced excitations were discussed. Numerical and analytical solutions of kinetic equations describing the model are discussed. The dynamics of light-induced magnetic anisotropy both uniaxial and cubic is analyzed.

• Received 16 January 2001

DOI:https://doi.org/10.1103/PhysRevB.64.064405