Charge-doping and chemical composition-driven magnetocrystalline anisotropy in CoPt core-shell alloy clusters

Abstract

Charge-doping together with 3d-4d alloying emerges as promising mechanisms for tailoring the magnetic properties of low-dimensional systems. Here, throughout ab initio calculations, we present a systematic overview regarding the impact of both electron(hole) charge-doping and chemical composition on the magnetocrystalline anisotropy (MA) of CoPt core-shell alloy clusters. By taking medium-sized Co_n Pt_m (N = n + m = 85) octahedral-like alloy nanoparticles for some illustrative core-sizes as examples, we found enhanced MA energies and large induced spin(orbital) moments in Pt-rich clusters. Moreover, depending on the Pt-core-size, both in-plane and off-plane directions of magnetization are observed. In general, the MA of these binary compounds further stabilizes upon charge-doping. In addition, in the clusters with small MA, the doping promotes magnetization switching. Insights into the microscopical origins of the MA behavior are associated to changes in the electronic structure of the clusters.

Graphical abstract

The magnetic properties of atomic-scale systems cannot be elucidated from their bulk counterparts. In particular, the magneto-crystallyne anisotropy energy (MAE), which arises mainly from the spin-orbit interactions is very sensitive to countless factors. The intricate behaviour comes from the interplay bounded by the strong chemical composition-dependence and the local environment. Here, we show that alloying together with charge-doping offers an appealing route for further tailoring the magnetic properties of cluster-alloys.

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