Magnetic anisotropy of $Co_x Pt_{1-x}$ clusters embedded in matrix: Influences of the cluster chemical composition and the matrix nature

TL;DR

This study investigates how the chemical composition of Co_xPt_{1-x} clusters and the nature of their embedding matrix influence their magnetic anisotropy, revealing significant effects from Pt content and oxide matrices on surface and volume anisotropy contributions.

Contribution

It provides a detailed analysis of magnetic anisotropy energy in Co-Pt clusters, highlighting the impact of Pt addition and matrix type on surface and volume anisotropy components.

Findings

15% Pt increases volume anisotropy significantly.

Oxide matrix enhances surface MAE due to CoO shell formation.

Surface and volume anisotropy contributions are separable and quantifiable.

Abstract

We report on the magnetic properties of Co$\_x$Pt$\_{1-x}$ clusters embedded in various matrices. Using a careful analysis of magnetization curves and ZFC susceptibility measurements, we determine the clusters magnetic anisotropy energy (MAE) and separate the surface and volume contributions. By comparing different chemical compositions, we show that a small amount of Pt (15%) induces an important increase in the volume anisotropy with respect to pure Co clusters, even in chemically disordered fcc clusters. Comparing the measurements of clusters embedded in Nb and MgO matrices, we show that the oxide matrix induces an important increase of the surface MAE attributed to the formation of an antiferromagnetic CoO shell around the clusters.