Topological electronic structure and intrinsic magnetization in MnBi$_4$Te$_7$: a Bi$_2$Te$_3$-derivative with a periodic Mn sublattice

TL;DR

This study identifies MnBi4Te7 as a topological material with intrinsic magnetization, combining non-trivial band topology and magnetic order, offering a platform for novel spintronic phenomena.

Contribution

It demonstrates that MnBi4Te7 has a band-inverted electronic structure with intrinsic net magnetization, filling a gap in topological magnetic materials.

Findings

MnBi4Te7 exhibits a topological surface state similar to Bi2Te3.

It has an antiferromagnetic phase below 13 K and a ferromagnetic-like phase below 5 K.

The material shows a complex magnetic phase diagram.

Abstract

Combinations of non-trivial band topology and long-range magnetic order hold promise for realizations of novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect. Following theoretical advances material candidates are emerging. Yet, a compound with a band-inverted electronic structure and an intrinsic net magnetization remains unrealized. MnBi$_2$Te$_4$ is a candidate for the first antiferromagnetic topological insulator and the progenitor of a modular (Bi$_2$Te$_3$)$_n$(MnBi$_2$Te$_4$) series. For $n$ = 1, we confirm a non-stoichiometric composition proximate to MnBi$_4$Te$_7$ and establish an antiferromagnetic state below 13 K followed by a state with net magnetization and ferromagnetic-like hysteresis below 5 K. Angle-resolved photoemission experiments and density-functional calculations reveal a topological surface state on the MnBi$_4$Te$_7$(0001) surface, analogous to the non-magnetic parent compound Bi$_2$Te$_3$. Our results render MnBi$_4$Te$_7$ as a band-inverted material with an intrinsic net magnetization and a complex magnetic phase diagram providing a versatile platform for the realization of different topological phases.