Nature of magnetic coupling between Mn ions in as-grown Ga$_{1-x}$Mn$_{x}$As studied by x-ray magnetic circular dichroism

TL;DR

This study uses x-ray magnetic circular dichroism to explore the magnetic interactions in as-grown GaMnAs, revealing short-range ferromagnetic correlations above the Curie temperature and the influence of interstitial Mn on magnetic properties.

Contribution

It provides new insights into the magnetic coupling mechanisms and the role of different Mn ions in GaMnAs using XMCD measurements.

Findings

Residual spin magnetic moments appear above T_C.

Short-range ferromagnetic correlations develop above T_C.

Antiferromagnetic interactions between Mn ions influence T_C.

Abstract

The magnetic properties of as-grown Ga$_{1-x}$Mn$_{x}$As have been investigated by the systematic measurements of temperature and magnetic field dependent soft x-ray magnetic circular dichroism (XMCD). The {\it intrinsic} XMCD intensity at high temperatures obeys the Curie-Weiss law, but residual spin magnetic moment appears already around 100 K, significantly above Curie temperature ($T_C$), suggesting that short-range ferromagnetic correlations are developed above $T_C$. The present results also suggest that antiferromagnetic interaction between the substitutional and interstitial Mn (Mn$_{int}$) ions exists and that the amount of the Mn$_{int}$ affects $T_C$.