Observing Spin Polarization of Individual Magnetic Adatoms

TL;DR

This study uses spin-polarized scanning tunneling spectroscopy to directly observe the spin-polarization states of individual Fe and Cr adatoms on Co nanoislands, revealing their exchange interactions and spin alignments.

Contribution

It provides direct experimental evidence of the spin polarization and exchange coupling of individual magnetic adatoms on a ferromagnetic surface, supported by first-principles calculations.

Findings

Fe adatoms exhibit parallel spin-polarization to Co surface state.

Cr adatoms exhibit antiparallel spin-polarization to Co surface state.

First-principles calculations predict opposite exchange interactions for Fe and Cr adatoms.

Abstract

We have used spin-polarized scanning tunneling spectroscopy to observe the spin-polarization state of individual Fe and Cr atoms adsorbed onto Co nanoislands. Both of these magnetic adatoms exhibit stationary out-of-plane spin-polarization due to their direct exchange interaction with the substrate, but the sign of the exchange coupling between electron states of the adatom and the surface state of the Co island is opposite for the two: Fe adatoms exhibit parallel spin-polarization to the Co surface state while Cr adatoms exhibit antiparallel spin-polarization. First-principles calculations predict ferromagnetic and antiferromagnetic alignment of the spin moment for individual Fe and Cr adatoms on a Co film, respectively, implying negative spin-polarization for Fe and Cr adatoms over the energy range of the Co surface state.