Strong single-ion anisotropy and anisotropic interactions of magnetic adatoms induced by topological surface states

TL;DR

This study uses density functional calculations to reveal that Fe adatoms on topological insulator Bi2Se3 exhibit strong magnetic anisotropy and anisotropic interactions mediated by topological surface states, with tunable Dzyaloshinskii-Moriya interactions.

Contribution

It demonstrates the significant role of topological surface states in inducing strong anisotropic magnetic interactions and single-ion anisotropy in Fe adatoms on Bi2Se3.

Findings

Fe adatoms show strong easy-axis magnetic anisotropy due to TSS.

The exchange interaction J exhibits RKKY behavior with anisotropy.

Dzyaloshinskii-Moriya interaction D can be enhanced by external electric fields.

Abstract

The nature of the magnetism brought about by Fe adatoms on the surface of the topological insulator Bi2Se3 was examined in terms of density functional calculations. The Fe adatoms exhibit strong easy-axis magnetic anisotropy in the dilute adsorption limit due to the topological surface states (TSS). The spin exchange J between the Fe adatoms follows a Ruderman-Kittel-Kasuya-Yosida (RKKY) behavior with substantial anisotropy, and the Dzyaloshinskii-Moriya (DM) interaction between them is quite strong with |D/J|~0.3 under the mediation by the TSS, and can be further raised to ~0.6 by an external electric field. The apparent single-ion anisotropy of a Fe adatom is indispensable in determining the spin orientation.