Spin and orbital magnetic moments of Fe in the $n$-type ferromagnetic semiconductor (In,Fe)As

TL;DR

This study investigates the magnetic moments of Fe in (In,Fe)As:Be using XAS and XMCD, revealing a significant orbital moment and hybridization effects, with evidence of ferromagnetic domain behavior.

Contribution

It provides detailed analysis of Fe magnetic moments and hybridization in (In,Fe)As:Be, highlighting the orbital contribution and magnetic domain behavior, which was not previously characterized.

Findings

Fe exhibits a larger orbital-to-spin magnetic moment ratio than Fe metal.

Fe 3d electrons are more than half-filled, indicating hybridization with host valence band.

Hysteretic behavior suggests the presence of discrete ferromagnetic domains.

Abstract

The electronic and magnetic properties of Fe atoms in the ferromagnetic semiconductor (In,Fe)As codoped with Be have been studied by x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) at the Fe $L_{2,3}$ edge. The XAS and XMCD spectra showed simple spectral line shapes similar to Fe metal, but the ratio of the orbital and spin magnetic moments ($M_\mathrm{orb}$/$M_\mathrm{spin}$) estimated using the XMCD sum rules was significantly larger than that of Fe metal, indicating a significant orbital moment of Fe $3d$ electrons in (In,Fe)As:Be. The positive value of $M_\mathrm{orb}$/$M_\mathrm{spin}$ implies that the Fe $3d$ shell is more than half-filled, which arises from the hybridization of the Fe$^{3+}$ ($d^5$) state with the charge-transfer $d^6\underline{L}$ states, where $\underline{L}$ is a ligand hole in the host valence band. The XMCD intensity as a function of magnetic field indicated hysteretic behavior of the superparamagnetic-like component due to discrete ferromagnetic domains.