Ultrafast laser-induced changes of the magnetic anisotropy in a low-symmetry iron garnet film

We explore a thermal mechanism of changing the magnetic anisotropy by using femtosecond laser pulses in a low-symmetry dielectric ferrimagnetic garnet (YBiPrLu)₃(FeGa)₅O₁₂ film grown on the (210)-type Gd₃Ga₅O₁₂ substrate as a model media. Employing spectral magneto-optical pump-probe technique and phenomenological analysis, we demonstrate that the magnetization precession in this film is a result of laser-induced changes of the growth-induced magnetic anisotropy along with the ultrafast inverse Faraday effect. The change of magnetic anisotropy relies on the lattice heating induced by laser pulses of any polarization on a picosecond time scale. We show that the orientation of the external magnetic field with respect to the magnetization easy plane affects the precession noticeably. Importantly, the relative contributions from the ultrafast inverse Faraday effect and the change of different growth-induced anisotropy parameters can be controlled varying the applied magnetic field strength and direction. As a result, the amplitude and the initial phase of the excited magnetization precession can be gradually tuned.