Vacancy and Antisite-Induced Ferromagnetism in Liquid-Phase Exfoliated Bi$_2$Te$_3$

TL;DR

This study demonstrates room-temperature ferromagnetism in liquid-phase exfoliated Bi$_2$Te$_3$, attributed to vacancies and antisites, with experimental and computational evidence showing bandgap modifications in thinner layers.

Contribution

It reveals the origin of ferromagnetism in exfoliated Bi$_2$Te$_3$ through combined experimental and DFT analysis, highlighting defect-induced magnetic properties.

Findings

Ferromagnetism observed at room temperature in exfoliated Bi$_2$Te$_3$

Vacancies and antisites cause magnetic behavior according to DFT

Bandgap broadening observed in thinner layers

Abstract

Bismuth Telluride (Bi$_2$Te$_3$) is a widely studied topological insulator, recognized for its unique surface states, low electronic bandgap, and low thermal conductivity. In this study, we characterize exfoliated Bi$_2$Te$_3$ dispersions produced via solvothermal intercalation, where ferromagnetism was measured at room temperature. DFT simulations show that this ferromagnetic behavior is attributed to the presence of vacancies and antisites in both the bulk material and the exfoliated crystals. Additionally, the DFT results were complemented by experimental measurements of the optical bandgap using UV-Vis spectroscopy, revealing a broadening of the bandgap as the material becomes thinner.