High Precision Magnetic Linear Dichroism Measurements in (Ga,Mn)As

TL;DR

This paper advances the measurement of second-order magneto-optical effects, specifically magnetic linear dichroism in (Ga,Mn)As, by comparing techniques and demonstrating a reliable method for spectral analysis over a broad energy range.

Contribution

It introduces a robust experimental approach for measuring magnetic linear dichroism in (Ga,Mn)As, enabling detailed spectral analysis of second-order MO effects.

Findings

MLD has a magnitude comparable to polar MOKE signals in (Ga,Mn)As

Four measurement techniques compared, with the harmonic and in-situ rotation method most reliable

MLD spectra measured from 0.1 eV to 2.7 eV in (Ga,Mn)As

Abstract

Investigation of magnetic materials using the first-order magneto-optical Kerr effects (MOKE) is well established and is frequently used in the literature. On the other hand, the utilization of the second-order (or quadratic) magneto-optical (MO) effects for the material research is rather rare. This is due to the small magnitude of quadratic MO signals and the fact that the signals are even in magnetization (i.e., they do not change a sign when the magnetization orientation is flipped), which makes it difficult to separate second-order MO signals from various experimental artifacts. In 2005 a giant quadratic MO effect - magnetic linear dichroism (MLD) - was observed in the ferromagnetic semiconductor (Ga,Mn)As. This discovery not only provided a new experimental tool for the investigation of in-plane magnetization dynamics in (Ga,Mn)As using light at normal incidence, but it also motivated the development of experimental techniques for the measurement of second-order MO effects in general. In this paper we compare four different experimental techniques that can be used to measure MLD and to separate it from experimental artifacts. We show that the most reliable results are obtained when the harmonic dependence of MLD on a mutual orientation of magnetization and light polarization plane is used together with the in-situ rotation of the sample followed by the magnetic field-induced rotation of magnetization. Using this technique we measure the MLD spectra of (Ga,Mn)As in a broad spectral range from 0.1 eV to 2.7 eV and we observe that MLD has a comparable magnitude as polar MOKE signals in this material.