The development of ferromagnetism in the doped topological insulator Bi2-xMnxTe3

TL;DR

This study investigates how doping Bi2Te3 with Mn induces ferromagnetism, revealing the magnetic transition, the substitution behavior of Mn, and the preservation of topological surface states with subtle modifications.

Contribution

It provides detailed experimental characterization of ferromagnetism development and surface state behavior in Mn-doped Bi2Te3, highlighting the coexistence of magnetism and topological surface states.

Findings

Ferromagnetism appears at specific Mn concentrations with Tc ~ 9-12 K.

Mn substitutes on Bi sites and is randomly distributed.

Topological surface states persist despite ferromagnetic doping.

Abstract

The development of ferromagnetism in Mn-doped Bi2Te3 is characterized through measurements on a series of single crystals with different Mn content. Scanning tunneling microscopy analysis shows that the Mn substitutes on the Bi sites, forming compounds of the type Bi2-xMnxTe3, and that the Mn substitutions are randomly distributed, not clustered. Mn doping first gives rise to local magnetic moments with Curie-like behavior, but by the compositions Bi1.96Mn0.04Te3 and Bi1.91Mn0.09Te3 a second order ferromagnetic transition is observed, with Tc ~ 9-12 K. The easy axis of magnetization in the ferromagnetic phase is perpendicular to the Bi2Te3 basal plane. Thermoelectric power and Hall effect measurements show that the Mn-doped Bi2Te3 crystals are p-type. Angle resolved photoemission spectroscopy measurements show that the topological surface states that are present in pristine Bi2Te3 are also present in ferromagnetic Mn-doped Bi2-xMnxTe3, and that the dispersion relations of the surface states are changed in a subtle fashion.