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

TL;DR

This study demonstrates that femtosecond laser pulses can induce ultrafast changes in magnetic anisotropy in a low-symmetry iron garnet film, enabling control over magnetization precession through thermal effects and external magnetic field orientation.

Contribution

It reveals a thermal mechanism for laser-induced magnetic anisotropy changes in low-symmetry garnets, combining experimental spectral magneto-optical analysis with phenomenological modeling.

Findings

Magnetization precession is triggered by laser-induced anisotropy changes and inverse Faraday effect.

Lattice heating mediates anisotropy change on a picosecond timescale.

Precession amplitude and phase can be tuned by magnetic field orientation and strength.

Abstract

We explore a thermal mechanism of changing the anisotropy by femtosecond laser pulses in dielectric ferrimagnetic garnets by taking a low symmetry (YBiPrLu)3(FeGa)5O12 film grown on the (210)-oriented Gd3Ga5O12 substrate as a model media. We demonstrate by means of spectral magneto-optical pump-probe technique and phenomenological analysis, that the magnetization precession in such a film is triggered by laser-induced changes of the growth-induced magnetic anisotropy along with the well-known ultrafast inverse Faraday effect. The change of magnetic anisotropy is mediated by the lattice heating induced by laser pulses of arbitrary polarization on a picosecond time scale. We show that the orientation of the external magnetic field with respect to the magnetization easy plane noticeably affects the precession excited via the anisotropy change. Importantly, the relative contributions from the ultrafast inverse Faraday effect and the change of different growth-induced anisotropy parameters can be controlled by 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.