Element-resolved orbital polarization in (III,Mn)As ferromagnetic semiconductors from $K$ edge x-ray magnetic circular dichroism

TL;DR

This study uses element-specific x-ray magnetic circular dichroism to analyze the orbital polarization of unoccupied states in (III,Mn)As ferromagnetic semiconductors, revealing how hole character varies with doping and metal-insulator transition.

Contribution

It provides the first element-resolved analysis of orbital polarization in (III,Mn)As, linking hole localization to doping levels and the metal-insulator transition.

Findings

XMCD at As K edge increases with Mn concentration

XMCD at Mn K edge shows concentration dependence and hole localization

Hole orbital magnetic moment transfers from Mn to As across the transition

Abstract

Using x-ray magnetic circular dichroism (XMCD), we determine the element-specific character and polarization of unoccupied states near the Fermi level in (Ga,Mn)As and (In,Ga,Mn)As thin films. The XMCD at the As K absorption edge consists of a single peak located on the low-energy side of the edge, which increases with the concentration of ferromagnetic Mn moments. The XMCD at the Mn K edge is more detailed and is strongly concentration-dependent, which is interpreted as a signature of hole localization for low Mn doping. The results indicate a markedly different character of the polarized holes in low-doped insulating and high-doped metallic films, with a transfer of the hole orbital magnetic moment from Mn to As sites on crossing the metal-insulator transition.