First-principles Calculations of Engineered Surface Spin Structures

TL;DR

This study uses density functional theory to analyze engineered surface spin structures, revealing their molecular magnet behavior, antiferromagnetic nature, and how local structure influences exchange interactions.

Contribution

It provides a detailed first-principles analysis of surface spin structures, accurately calculating exchange couplings and explaining their variations based on local atomic arrangements.

Findings

Mn atoms form surface molecular magnets

Exchange couplings match experimental values within 8%

Local structure determines exchange interaction variations

Abstract

The engineered spin structures recently built and measured in scanning tunneling microscope experiments are calculated using density functional theory. By determining the precise local structure around the surface impurities, we find the Mn atoms can form molecular structures with the binding surface, behaving like surface molecular magnets. The spin structures are confirmed to be antiferromagnetic, and the exchange couplings are calculated within 8% of the experimental values simply by collinear-spin GGA+U calculations. We can also explain why the exchange couplings significantly change with different impurity binding sites from the determined local structure. The bond polarity is studied by calculating the atomic charges with and without the Mn adatoms.