First-principles investigation of the very large Perpendicular Magnetic Anisotropy at Fe|MgO Interfaces

TL;DR

This study uses first-principles calculations to reveal the origin of large perpendicular magnetic anisotropy at Fe|MgO interfaces, showing how orbital hybridization and oxidation levels influence PMA strength, aligning with experimental data.

Contribution

It provides a detailed atomic-level understanding of the origin of large PMA at Fe|MgO interfaces and how oxidation and disorder affect its magnitude.

Findings

PMA up to 3 erg/cm² at Fe|MgO interfaces.

PMA originates from specific orbital hybridizations involving O-$p_z$ and Fe $d$ orbitals.

Over- or underoxidation reduces PMA due to orbital overlap disruption.

Abstract

The perpendicular magnetic anisotropy (PMA) arising at the interface between ferromagnetic transition metals and metallic oxides are investigated via first-principles calculations. In this work very large values of PMA up to 3 erg/cm$^2$ at Fe$|$MgO interfaces are reported in agreement with recent experiments. The origin of PMA is attributed to overlap between O-$p_z$ and transition metal $d_{z^2}$ orbitals hybridized with $d_{xz(yz)}$ orbitals with stronger spin-orbit coupling induced splitting around the Fermi level for perpendicular magnetization orientation. Furthemore, it is shown that the PMA value weakens in case of over- or underoxidation when oxygen $p_z$ and transition metal $d_{z^2}$ orbitals overlap is strongly affected by disorder, in agreement with experimental observations in magnetic tunnel junctions.