Photo-induced precession of magnetization in ferromagnetic (Ga,Mn)As

TL;DR

This paper reports the observation of photo-induced magnetization precession in ferromagnetic (Ga,Mn)As using time-resolved magneto-optical techniques, linking it to non-equilibrium carrier dynamics affecting magnetic anisotropy.

Contribution

It demonstrates the occurrence of magnetization precession induced by optical pulses in (Ga,Mn)As and models it with gyromagnetic theory considering carrier-related anisotropy changes.

Findings

Magnetization precession observed via time-resolved measurements.

Precession explained by gyromagnetic theory with impulsive magnetic field change.

Carrier dynamics influence magnetic anisotropy and precession behavior.

Abstract

Precession of magnetization induced by pulsed optical excitation is observed in a ferromagnetic semiconductor (Ga,Mn)As by time-resolved magneto-optical measurements. It appears as complicated oscillations of polarization plane of linearly-polarized probe pulses, but is reproduced by gyromagnetic theory incorporating an impulsive change in an effective magnetic field due to changes in magnetic anisotropy. It is inferred from the shape of the impulse that the changes in anisotropy result from non-equilibrium carrier population: cooling of hot photo-carriers and subsequent annihilation of photo-carriers.