Effect of Pt impurities on the magnetocrystalline anisotropy of hcp Co: a first-principles study

TL;DR

This study uses first-principles calculations to explore how platinum impurities affect the magnetocrystalline anisotropy energy in hexagonal cobalt, revealing concentration-dependent changes and long-range oscillations.

Contribution

It provides detailed insights into the impact of Pt impurities on Co's MAE using relativistic first-principles methods, highlighting the role of Friedel oscillations.

Findings

At low Pt concentrations, MAE decreases.

At higher Pt concentrations, MAE increases.

Long-range Friedel oscillations influence MAE size effects.

Abstract

In terms of the fully relativistic screened Korringa-Kohn-Rostoker method we investigate the variation in the magnetocrystalline anisotropy energy (MAE) of hexagonal close-packed cobalt with the addition of platinum impurities. In particular, we perform calculations on a bulk cobalt system in which one of the atomic layers contains a fractional, substitutional platinum impurity. Our calculations show that at small concentrations of platinum the MAE is reduced, while at larger concentrations the MAE is enhanced. This change of the MAE can be attributed to an interplay between on-site Pt MAE contributions and induced MAE contributions on the Co sites. The latter ones are subject to pronounced, long-ranged Friedel-oscillations that can lead to significant size effects in the experimental determination of the MAE of nano-sized samples.