First-principles investigation of magnetocrystalline anisotropy oscillations in Co$_{2}$FeAl/Ta heterostructures

TL;DR

This study uses first-principles calculations to reveal how quantum well states in Ta capping layers cause oscillations in magnetocrystalline anisotropy energy in Co2FeAl/Ta heterostructures, enabling potential control of magnetic properties.

Contribution

It demonstrates that quantum well states significantly influence MCAE oscillations, providing new insights into tuning magnetic anisotropy in heterostructures.

Findings

MCAE oscillates with Ta layer thickness due to quantum well states.

Oscillation magnitude varies with interface structure, larger at FeAl interface.

Quantum well effects dominate MCAE behavior, not just local interface properties.

Abstract

We report first-principles investigations of magnetocrystalline anisotropy energy (MCAE) oscillations as a function of capping layer thickness in Heusler alloy Co\textsubscript{2}FeAl/Ta heterostructures. Substantial oscillation is observed in FeAl-interface structure. According to $k$-space and band-decomposed charge density analyses, this oscillation is mainly attributed to the Fermi-energy-vicinal quantum well states (QWS) which are confined between Co\textsubscript{2}FeAl/Ta interface and Ta/vacuum surface. The smaller oscillation magnitude in the Co-interface structure can be explained by the smooth potential transition at the interface. These findings clarify that MCAE in Co\textsubscript{2}FeAl/Ta is not a local property of the interface and that the quantum well effect plays a dominant role in MCAE oscillations of the heterostructures. This work presents the possibility of tuning MCAE by QWS in capping layers, and paves the way for artificially controlling magnetic anisotropy energy in magnetic tunnel junctions.