Unravelling the Local Crystallographic Structure of Ferromagnetic Ga$_y$Fe$_{4-y}$N Nanocrystals Embedded in GaN

TL;DR

This study uses advanced x-ray techniques to analyze the local structure of Ga$_y$Fe$_{4-y}$N nanocrystals in GaN, revealing how growth conditions influence their atomic arrangement and magnetic properties.

Contribution

It introduces a novel experimental approach combining anomalous x-ray diffraction and diffraction anomalous fine structure to determine local atomic arrangements in embedded nanocrystals.

Findings

Ga atoms can occupy 3c positions at the faces of the fcc lattice up to 30%

The Curie temperature of nanocrystals increases from 450 K to 500 K with Ga occupation

The experimental protocol effectively reveals local structures in magnetic multi-phase systems

Abstract

In the Fe-doped GaN phase-separated magnetic semiconductor GaFeN, the presence of embedded Ga$_y$Fe$_{4-y}$N nanocrystals determines the magnetic properties of the system. Here, through a combination of anomalous x-ray diffraction and diffraction anomalous fine structure, the local structure of Ga in self-assembled face-centered cubic (fcc) Ga$_y$Fe$_{4-y}$N nanocrystals embedded in wurtzite GaN thin layers is investigated in order to shed light onto the correlation between fabrication parameters, local structural arrangement and overall magnetic properties of the material system. It is found, that by adjusting the growth parameters and thus, the crystallographic surroundings, the Ga atoms can be induced to incorporate into 3$c$ positions at the faces of the fcc crystal lattice, reaching a maximum occupancy of 30\%. The magnetic response of the embedded nanocrystals is ferromagnetic with Curie temperature increasing from 450\,K to 500\,K with the Ga occupation. These results demonstrate the outstanding potential of the employed experimental protocol for unravelling the local structure of magnetic multi-phase systems, even when embedded in a matrix containing the same element under investigation.