Room temperature p-induced surface ferromagnetism

TL;DR

This paper demonstrates that oxygen-terminated ZnO surfaces exhibit stable ferromagnetism at room temperature due to p-hole induced magnetic order, suggesting a universal mechanism for ionic oxides.

Contribution

It provides first-principles evidence of room temperature surface ferromagnetism in ZnO and introduces a universal mechanism applicable to ionic oxides for designing magnetic nanostructures.

Findings

Surface ferromagnetism stable at 300 K and above

Half-metallicity observed in the surface states

Long-range magnetic order driven by p-holes in the valence band

Abstract

We prove a spontaneous magnetization of the oxygen-terminated ZnO (0001) surface by utilizing a multi-code, SIESTA and KKR, first-principles approach, involving both LSDA+U and selfinteraction corrections (SIC) to treat electron correlation effects. Critical temperatures are estimated from Monte Carlo simulations, showing that at and above 300 K the surface is thermodynamically stable and ferromagnetic. The observed half-metallicity and long-range magnetic order originate from the presence of p-holes in the valence band of the oxide. The mechanism is universal in ionic oxides and points to a new route for the design of ferromagnetic low dimensional systems.