Hidden-anisotropy-induced $\pi$ phase shift in all-optical magnetization precession

TL;DR

This study reveals that the phase shift in laser-induced magnetization precession in Pt/Co/Pt films is influenced by hidden interface anisotropy dependent on phonon temperature, requiring an augmented model for accurate description.

Contribution

The paper introduces a microscopic model accounting for hidden interface anisotropy's dependence on phonon temperature, explaining the observed $\pi$ phase shift in magnetization precession.

Findings

The $\pi$ phase shift is explained by hidden interface anisotropy.

Both electron and phonon temperatures influence the precession phase.

An augmented microscopic model accurately describes the experimental data.

Abstract

Laser-induced magnetization precession of an in-plane magnetized Pt/Co/Pt film with perpendicular interface anisotropy was studied using time resolved magneto-optical Kerr effect. An additional $\pi$ shift in the phase of precession is needed to describe the measured data if only the demagnetization energy is considered. Based on an augmented microscopic model description of the laser-induced magnetization dynamics, the additional $\pi$ phase is found to be rendered by the dependence on the phonon temperature of the hidden interface anisotropy, in contrast to the dependence on the electron temperature of the demagnetization energy. The observation that the phase of precession is affected by both the electron and the phonon temperature warrants a detailed knowledge about the forms of anisotropy present in the system under investigation for a holistic description of laser-induced magnetization precession.