Experimental probing of exchange interactions between localized spins in the dilute magnetic insulator (Ga,Mn)N

TL;DR

This study experimentally investigates the exchange interactions between Mn ions in dilute magnetic insulator (Ga,Mn)N, confirming theoretical predictions and showing a change from ferromagnetic to antiferromagnetic coupling based on Mn charge state.

Contribution

It provides detailed experimental data on exchange interactions in (Ga,Mn)N, verifying ab initio predictions and revealing the influence of Mn charge states on magnetic coupling.

Findings

Exchange interactions depend on Mn charge state.

Ferromagnetic to antiferromagnetic transition observed.

Experimental results align with theoretical predictions.

Abstract

The sign, magnitude, and range of the exchange couplings between pairs of Mn ions is determined for (Ga,Mn)N and (Ga,Mn)N:Si with x < 3%. The samples have been grown by metalorganic vapor phase epitaxy and characterized by secondary-ion mass spectroscopy; high-resolution transmission electron microscopy with capabilities allowing for chemical analysis, including the annular dark-field mode and electron energy loss spectroscopy; high-resolution and synchrotron x-ray diffraction; synchrotron extended x-ray absorption fine-structure; synchrotron x-ray absorption near-edge structure; infra-red optics and electron spin resonance. The results of high resolution magnetic measurements and their quantitative interpretation have allowed to verify a series of ab initio predictions on the possibility of ferromagnetism in dilute magnetic insulators and to demonstrate that the interaction changes from ferromagnetic to antiferromagnetic when the charge state of the Mn ions is reduced from 3+ to 2+.