Nonlocal orbital magnetism of 3d adatoms deposited on the Pt(111) surface

TL;DR

This paper investigates the nonlocal orbital magnetism induced in Pt(111) surface by 3d adatoms, revealing significant nonlocal contributions to orbital moments through first-principles calculations involving spin-orbit coupling.

Contribution

It introduces a first-principles approach to describe the nonlocal orbital magnetism in adatom-surface systems, highlighting the role of charge current density and spin-orbit susceptibility.

Findings

Nonlocal orbital moments extend three times farther than spin and local orbital moments.

Nonlocal contributions are as large as local orbital moments.

Spin-orbit susceptibility in Pt surface drives nonlocal orbital magnetism.

Abstract

The orbital magnetic moment is still surprisingly not well understood, in contrast to the spin part. Its description in finite systems, such as isolated atoms and molecules, is not problematic, but it was only recently that a rigorous picture was provided for extended systems. Here we focus on an intermediate class of systems: magnetic adatoms placed on a non-magnetic surface. We show that the essential quantity is the ground-state charge current density, in the presence of spin-orbit coupling, and set out its first-principles description. This is illustrated by studying the magnetism of the surface Pt electrons, induced by the presence of Cr, Mn, Fe, Co and Ni adatoms. A physically appealing partition of the charge current is introduced. This reveals that there is an important nonlocal contribution to the orbital moments of the Pt atoms, extending three times as far from each magnetic adatom as the induced spin and local orbital moments. We find that it is as sizable as the latter, and attribute its origin to a spin-orbital susceptibility of the Pt surface, different from the one responsible for the formation of the local orbital moments.