Oxygen vacancy enhanced room temperature ferromagnetism in Al-doped MgO nanoparticles

TL;DR

This study demonstrates that oxygen vacancies significantly contribute to room temperature ferromagnetism in Al-doped MgO nanoparticles, with vacancy concentration and magnetic properties enhanced by vacuum annealing.

Contribution

It reveals the role of oxygen vacancies in inducing ferromagnetism in Al-doped MgO nanoparticles and shows how annealing increases vacancy concentration and magnetic response.

Findings

Maximum saturation magnetization of 0.023 emu/g at 2 at.% Al

Oxygen vacancies increase with vacuum annealing

Vacancy concentration correlates with ferromagnetic strength

Abstract

We have investigated the room temperature ferromagnetic order that develops in Al-substituted magnesium oxide, Mg(Al)O, nanoparticles with Al fractions of up to 5 at.%. All samples, including undoped MgO nanoparticles, exhibit room temperature ferromagnetism, with the saturation magnetization reaching a maximum of 0.023 emu/g at 2 at.% of Al. X-ray photoelectron spectroscopy identifies the presence of oxygen vacancies in both doped and undoped MgO nanoparticles, with the vacancy concentration increasing upon vacuum annealing of Mg(Al)O, resulting in two-fold enhancement of the saturation magnetization for 2 at.% Al-doped MgO. Our results suggest that the oxygen vacancies are largely responsible for room temperature ferromagnetism in MgO.