X-ray magnetic circular dichroism characterization of GaN/Ga1-xMnxN digital ferromagnetic heterostructure

TL;DR

This study uses soft x-ray absorption spectroscopy and XMCD to analyze the magnetic properties of GaN/Ga1-xMnxN heterostructures, revealing coexistence of paramagnetic and ferromagnetic Mn ions and confirming the origin of ferromagnetism.

Contribution

It provides direct spectroscopic evidence that ferromagnetism in GaN/Ga1-xMnxN heterostructures arises from substitutional Mn2+ ions, not from ferromagnetic precipitates.

Findings

Ferromagnetic behavior linked to substitutional Mn2+ ions.

Coexistence of paramagnetic and ferromagnetic Mn in layers.

XMCD spectra show differences between ferromagnetic and paramagnetic Mn states.

Abstract

We have investigated the magnetic properties of a GaN/Ga1-xMnxN (x = 0.1) digital ferromagnetic heterostructure (DFH) showing ferromagnetic behavior using soft x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD). The Mn L2,3-edge XAS spectra were similar to those of Ga1-xMnxN random alloy thin films, indicating a substitutional doping of high concentration Mn into GaN. From the XMCD measurements, it was revealed that paramagnetic and ferromagnetic Mn atoms coexisted in the Ga1-xMnxN digital layers. The ferromagnetic moment per Mn atom estimated from XMCD agreed well with that estimated from SQUID measurements. From these results, we conclude that the ferromagnetic behavior of the GaN/Ga1-xMnxN DFH sample arises only from substitutional Mn2+ ions in the Ga1-xMnxN digital layers and not from ferromagnetic precipitates. Subtle differences were also found from the XMCD spectra between the electronic states of the ferromagnetic and paramagnetic Mn2+ ions.