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.
Highlights
Soon after the discovery of topological insulators (TIs) a decade ago [1], the role of magnetism and its potential to modify the electronic topology emerged as a central issue in the field of topological materials
It is recognized that the interplay between magnetic order and electronic topology offers a rich playground for the realization of exotic topological states of matter, such as the quantum anomalous Hall state [2,3], the axion insulator state [4,5,6], and magnetic Weyl and nodal-line semimetals [7,8,9,10,11], enabling in turn different routes to spintronic applications [12,13,14]
We present a comprehensive study of structural, magnetic, and electronic properties of the Bi2Te3-derivative Mn0.75ð3ÞBi4.17ð3ÞTe7, i.e., the (n 1⁄4 1)-member Mn147 of the modular ðBi2Te3ÞnðMnBi2Te4Þ series
Summary
Soon after the discovery of topological insulators (TIs) a decade ago [1], the role of magnetism and its potential to modify the electronic topology emerged as a central issue in the field of topological materials. Initiated by works on epitaxial MnBi2Se4 layers [19,20], the compound MnBi2Te4 has recently arisen as the first derivative of Bi2Te3 that hosts structurally and magnetically ordered Mn atoms on well-defined crystallographic sites [21,22,23,24]. MnBi2Te4 provides the first example of an intrinsic magnetic TI [23,28,30,31] In this joint experimental and theoretical work we establish another ternary manganese-bismuth telluride, MnBi4Te7, i.e., the (n 1⁄4 1) member of a modular ðBi2Te3ÞnðMnBi2Te4Þ series, as the first instance of a compound that features both an inverted electronic band structure and an intrinsic net magnetization. We observe several competing magnetic states in MnBi4Te7 which, in combination with the presence of topological surface states, could provide a versatile platform for tunability between different topological regimes
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