Origin of the large interfacial perpendicular magnetic anisotropy in MgO/Co2FeAl

Abstract

Interfacial perpendicular magnetic anisotropy in the $\mathrm{MgO}/{\mathrm{Co}}_{2}\mathrm{FeAl}$ heterostructure is desired for technological applications, while the origin of the large interfacial anisotropy constant ${K}_{i}$ remains controversial. Here we show that, by modeling four types of interface models for the $\mathrm{MgO}/{\mathrm{Co}}_{2}\mathrm{FeAl}$ system using first-principles calculations, the $\mathrm{MgO}/{\mathrm{Co}}_{2}$ interface is energetically more favorable than the MgO/FeAl interface and the interfacial Co atoms at the former interface produce out-of-plane ${K}_{i}$, while the interfacial Fe atoms at the latter interface produce in-plane ${K}_{i}$. The origin of these different behaviors can be explained by the atomic-resolved and orbital-resolved ${K}_{i}$ along with the perturbation theory energy analysis. In addition, we also studied the influence of 26 capping layers on the interfacial magnetic anisotropy of $\mathrm{MgO}/{\mathrm{Co}}_{2}\mathrm{FeAl}$ and found that Fe and W capping can significantly enhance ${K}_{i}$ in the $\mathrm{MgO}/{\mathrm{Co}}_{2}\mathrm{FeAl}$ with a particularly large ${K}_{i}$ of $4.90\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}/{\mathrm{m}}^{2}$ in the W-capped model. This work clarifies the atomistic origin of the interfacial perpendicular magnetic anisotropy and provides guidance to further enhance interfacial ${K}_{i}$ by adding capping layers in the $\mathrm{MgO}/{\mathrm{Co}}_{2}\mathrm{FeAl}$.