Abstract
Using single-crystal neutron diffraction, we present a systematic investigation of the crystal structure and magnetism of the van der Waals topological insulators MnBi2Te4 and MnBi4Te7, where rich topological quantum states have been recently predicted and observed. Structural refinements reveal that considerable Bi atoms occupied on the Mn sites in both materials, distinct from the previously reported antisite disorder. We show unambiguously that MnBi2Te4 orders antiferromagnetically below 24 K, featured by a magnetic symmetry RI-3c, while MnBi4Te7 is antiferromagnetic below 13 K with a magnetic space group Pc-3c1. They both present antiferromagnetically coupled ferromagnetic layers with spins along the c axis. We put forward a stacking rule for the crystal structure of an infinitely adaptive series MnBi2nTe3n+1 (n≥1) with a building unit of [Bi2Te3]. By comparing the magnetic properties between MnBi2Te4 and MnBi4Te7, together with recent density-functional theory calculations, we concluded that a two-dimensional magnetism limit might be realized in the derivatives. Our work may promote theoretical studies of topological magnetic states in the series of MnBi2nTe3n+1.
Original language | English |
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Article number | 020412 |
Journal | Physical Review B |
Volume | 101 |
Issue number | 2 |
DOIs | |
State | Published - Jan 27 2020 |
Funding
Acknowledgments. We thank C. D. Batista for useful discussions. The research at Oak Ridge National Laboratory (ORNL) was supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Early Career Research Program Award No. KC0402010, under Contract No. DE-AC05-00OR22725 and the U.S. DOE, Office of Science User Facility operated by the ORNL. Work at UCLA was supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences under Award No. DE-SC0011978. The U.S. Government retains, and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan .