Title: Crystal and magnetic structures of magnetic topological insulators MnBi₂Te₄ and MnBi₄Te₇

Abstract

Using single-crystal neutron diffraction, we present a systematic investigation of the crystal structure and magnetism of the van der Waals topological insulators ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$ and ${\mathrm{MnBi}}_4{\mathrm{Te}}_7$, 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 ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$ orders antiferromagnetically below 24 K, featured by a magnetic symmetry $R_I\text{-}3c$, while ${\mathrm{MnBi}}_4{\mathrm{Te}}_7$ is antiferromagnetic below 13 K with a magnetic space group $P_c\text{-}3c1$. 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 ${\mathrm{MnBi}}_{2n}{\mathrm{Te}}_{3n+1}$ ( $n\ge 1$) with a building unit of $\left[{\mathrm{Bi}}_2{\mathrm{Te}}_3\right]$. Overall, by comparing the magnetic properties between ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$ and ${\mathrm{MnBi}}_4{\mathrm{Te}}_7$, 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 ${\mathrm{MnBi}}_{2n}{\mathrm{Te}}_{3n+1}$.

Authors:

Ding, Lei  ^[1];

• Search DOE PAGES for author "Ding, Lei"
• Search DOE PAGES for ORCID "0000-0002-1556-2095"

Hu, Chaowei ^[2]; Ye, Feng  ^[1];

• Search DOE PAGES for author "Ye, Feng"
• Search DOE PAGES for ORCID "0000-0001-7477-4648"

Feng, Erxi  ^[1];

• Search DOE PAGES for author "Feng, Erxi"
• Search DOE PAGES for ORCID "0000-0002-3703-1164"

Ni, Ni ^[2]; Cao, Huibo  ^[1]

• Search DOE PAGES for author "Cao, Huibo"
• Search DOE PAGES for ORCID "0000-0002-5970-4980"

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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Univ. of California, Los Angeles, CA (United States). California NanoSystems Inst.

Publication Date:

Mon Jan 27 00:00:00 EST 2020

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1761702

Grant/Contract Number:  

AC05-00OR22725; KC0402010; SC0011978

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review B

Additional Journal Information:

Journal Volume: 101; Journal Issue: 2; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; magnetism; strongly correlated systems; topological materials; magnetization measurements; neutron diffraction; specific heat measurements