Theory of magnetization precession induced by a picosecond strain pulse in ferromagnetic semiconductor (Ga,Mn)As

TL;DR

This paper presents a theoretical model describing how a picosecond strain pulse induces magnetization precession in ferromagnetic (Ga,Mn)As, highlighting the roles of anisotropy, layer thickness, and pulse parameters.

Contribution

It develops a quantitative Landau-Lifshitz-based model for magnetization precession caused by strain pulses in ferromagnetic semiconductors, including numerical analysis for specific geometries.

Findings

Precession amplitude depends on magnetocrystalline anisotropy.

Layer thickness influences the precession response.

Strain pulse parameters critically affect the excitation of precession.

Abstract

A theoretical model of the coherent precession of magnetization excited by a picosecond acoustic pulse in a ferromagnetic semiconductor layer of (Ga,Mn)As is developed. The short strain pulse injected into the ferromagnetic layer modifies the magnetocrystalline anisotropy resulting in a tilt of the equilibrium orientation of magnetization and subsequent magnetization precession. We derive a quantitative model of this effect using the Landau-Lifshitz equation for the magnetization that is precessing in the time-dependent effective magnetic field. After developing the general formalism, we then provide a numerical analysis for a certain structure and two typical experimental geometries in which an external magnetic field is applied either along the hard or the easy magnetization axis. As a result we identify three main factors, which determine the precession amplitude: the magnetocrystalline anisotropy of the ferromagnetic layer, its thickness, and the strain pulse parameters.