Dirac-Electrons-Mediated Magnetic Proximity Effect in Topological Insulator / Magnetic Insulator Heterostructures

TL;DR

This study demonstrates Dirac electrons mediating magnetic proximity effects in topological insulator/magnetic insulator heterostructures, with tunable magnetism via electrical gating, advancing potential low-power spintronic applications.

Contribution

It provides experimental evidence of Dirac-electron-mediated magnetic proximity effect and introduces a model explaining the influence of carrier density on magnetism.

Findings

Maximized proximity-induced magnetism near charge neutrality point.

Suppressed magnetism at high carrier density explained by diamagnetic screening.

Potential for low-power spintronic device applications.

Abstract

The possible realization of dissipationless chiral edge current in a topological insulator / magnetic insulator heterostructure is based on the condition that the magnetic proximity exchange coupling at the interface is dominated by the Dirac surface states of the topological insulator. Here we report a polarized neutron reflectometry observation of Dirac electrons mediated magnetic proximity effect in a bulk-insulating topological insulator (Bi$_{0.2}$Sb$_{0.8}$)$_{2}$Te$_{3}$ / magnetic insulator EuS heterostructure. We are able to maximize the proximity induced magnetism by applying an electrical back gate to tune the Fermi level of topological insulator to be close to the charge neutral point. A phenomenological model based on diamagnetic screening is developed to explain the suppressed proximity induced magnetism at high carrier density. Our work paves the way to utilize the magnetic proximity effect at the topological insulator/magnetic insulator hetero-interface for low-power spintronic applications.