Out- versus in-plane magnetic anisotropy of free Fe and Co nanocrystals: tight-binding and first-principles studies

TL;DR

This study compares the magnetic anisotropy of free Fe and Co nanocrystals using tight-binding and DFT calculations, revealing element-specific easy axes and implications for magnetic storage applications.

Contribution

It provides a detailed analysis of the magnetic anisotropy in Fe and Co nanocrystals, highlighting the dominant role of (001) facets and the contrasting easy axes.

Findings

Fe nanocrystals have out-of-plane easy axis.

Co nanocrystals have in-plane easy axis.

Fe nanocrystals exhibit high uniaxial anisotropy.

Abstract

We report tight-binding (TB) and Density Function Theory (DFT) calculations of magnetocrystalline anisotropy energy (MAE) of free Fe (body centerd cubic) and Co (face centered cubic) slabs and nanocrystals. The nanocrystals are truncated square pyramids which can be obtained experimentally by deposition of metal on a SrTiO$_3$(001) substrate. For both elements our local analysis shows that the total MAE of the nanocrystals is largely dominated by the contribution of (001) facets. However, while the easy axis of Fe(001) is out-of-plane, it is in-plane for Co(001). This has direct consequences on the magnetic reversal mechanism of the nanocrystals. Indeed, the very high uniaxial anisotropy of Fe nanocrystals makes them a much better potential candidate for magnetic storage devices.