Magnetism and half-metallicity at the O surfaces of ceramic oxides

TL;DR

This study demonstrates that certain ceramic oxide surfaces can exhibit spin-polarization and half-metallicity due to surface oxygen atoms, revealing potential for magnetic applications in non-magnetic insulators.

Contribution

It provides ab-initio evidence of surface-induced magnetism and half-metallicity in ZrO₂, Al₂O₃, and MgO, highlighting the role of oxygen surface states.

Findings

Large spin moments up to 1.56 μ_B at O surfaces

Surface oxygen atoms host the magnetic moments

Magnetization linked to surface charge loss

Abstract

The occurence of spin-polarization at ZrO$_{2}$, Al$_{2}$O$_{3}$ and MgO surfaces is proved by means of \textit{ab-initio} calculations within the density functional theory. Large spin moments, as high as 1.56 $\mu_B$, develop at O-ended polar terminations, transforming the non-magnetic insulator into a half-metal. The magnetic moments mainly reside in the surface oxygen atoms and their origin is related to the existence of $2p$ holes of well-defined spin polarization at the valence band of the ionic oxide. The direct relation between magnetization and local loss of donor charge makes possible to extend the magnetization mechanism beyond surface properties.