Local Environment of Ferromagnetically Ordered Mn in Epitaxial InMnAs

TL;DR

This study investigates the local environment and magnetic properties of Mn in epitaxial InMnAs using x-ray spectroscopy, revealing localized Mn states, two ferromagnetic species, and ruling out MnAs clusters as the source of ferromagnetism.

Contribution

It provides detailed spectroscopic analysis of Mn in InMnAs, identifying two ferromagnetic species and clarifying the local atomic environment of Mn.

Findings

Mn exhibits localized 3d states consistent with atomic Mn2+

Two ferromagnetic species with different transition temperatures identified

Ferromagnetism not due to MnAs clusters

Abstract

The magnetic properties of the ferromagnetic semiconductor In0.98Mn0.02As were characterized by x-ray absorption spectroscopy and x-ray magnetic circular dichroism. The Mn exhibits an atomic-like L2,3 absorption spectrum that indicates that the 3d states are highly localized. In addition, a large dichroism at the Mn L2,3 edge was observed from 5-300 K at an applied field of 2T. A calculated spectrum assuming atomic Mn2+ yields the best agreement with the experimental InMnAs spectrum. A comparison of the dichroism spectra of MnAs and InMnAs show clear differences suggesting that the ferromagnetism observed in InMnAs is not due to hexagonal MnAs clusters. The temperature dependence of the dichroism indicates the presence of two ferromagnetic species, one with a transition temperature of 30 K and another with a transition temperature in excess of 300 K. The dichroism spectra are consistent with the assignment of the low temperature species to random substitutional Mn and the high temperature species to Mn near-neighbor pairs.