# Demonstration of defect-defect ferromagnetic coupling in Gd doped GaN epitaxial films: A polarization selective magneto-photoluminescence study

## TL;DR

This study demonstrates that Gd doping in GaN epitaxial films induces defect-related ferromagnetic coupling, confirmed through polarization selective magneto-photoluminescence measurements at low temperature.

## Contribution

It provides experimental evidence of defect-defect ferromagnetic coupling in Gd-doped GaN, a novel insight into magnetic interactions in this material system.

## Key findings

- Gd doping creates three types of donor-like defects in GaN.
- Defects exhibit ferromagnetic coupling, evidenced by spin-flip scattering behavior.
- Co-doping with Si does not affect the defect coupling.

## Abstract

Magnetic field dependent polarization selective photoluminescence(PL) study has been carried out at 1.5~K on Gd-doped GaN epitaxial layers grown on c-SiC substrates by molecular beam epitaxy technique. It has been found that the incorporation of Gd in GaN leads to the generation of three types of donor like defects that result in neutral donor bound excitonic features in low temperature PL. The study reveals that the rate of spin-flip scattering for all the three excitonic features becomes almost $B$-independent suggesting that these signals must be stemming from defects which are ferromagnetically coupled with each other. This is further confirmed by the study carried out on a GaN sample co-doped with Si and Gd, where defects are found to be ferromagnetically coupled, while Si-donors do not show any involvement in coupling.