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arXiv · 2204.09420

Ferromagnetic-antiferromagnetic coexisting ground states and exchange bias effects in $\bf{MnBi_4Te_7}$ and $\bf{MnBi_6Te_{10}}$

Xiaolong Xu·Shiqi Yang·Huan Wang·Roger Guzman·Yaozheng Zhu·Yuxuan Peng·Zhihao Zang·Ming Xi·Shangjie Tian·Yanping Li·Hechang Lei·Zhaochu Luo·Jinbo Yang·Tianlong Xia·Wu Zhou·Yuan Huang·Yu Ye
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Abstract

Natural superlattice structures $\rm{(MnBi_2Te_4)(Bi_2Te_3)}$$_n$ ($n$ = 1, 2,...), in which magnetic $\rm{MnBi_2Te_4}$ layers are separated by nonmagnetic $\rm{Bi_2Te_3}$ layers, hold band topology, magnetism and reduced interlayer coupling, providing a promising platform for the realization of exotic topological quantum states. However, their magnetism in the two-dimensional limit, which is crucial for further exploration of quantum phenomena, remains elusive. Here, complex ferromagnetic (FM)-antiferromagnetic (AFM) coexisting ground states that persist up to the 2-septuple layers (SLs) limit are observed and comprehensively investigated in $\rm{MnBi_4Te_7}$ ($n$ = 1) and $\rm{MnBi_6Te_{10}}$ ($n$ = 2). The ubiquitous Mn-Bi site mixing modifies or even changes the sign of the subtle inter-SL magnetic interactions, yielding a spatially inhomogeneous interlayer coupling. Further, a tunable exchange bias effect is observed in $\rm{(MnBi_2Te_4)(Bi_2Te_3)}$$_n$ ($n$ = 1, 2), arising from the coupling between the FM and AFM components in the ground state. Our work highlights a new approach toward the fine-tuning of magnetism and paves the way for further study of quantum phenomena in $\rm{(MnBi_2Te_4)(Bi_2Te_3)}$$_n$ ($n$ = 1, 2,...) as well as their magnetic applications.

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Xiaolong Xu, Shiqi Yang, Huan Wang, Roger Guzman, Yaozheng Zhu, Yuxuan Peng, Zhihao Zang, Ming Xi, Shangjie Tian, Yanping Li, Hechang Lei, Zhaochu Luo, Jinbo Yang, Tianlong Xia, Wu Zhou, Yuan Huang, Yu Ye. 2022-04-20. Ferromagnetic-antiferromagnetic coexisting ground states and exchange bias effects in $\bf{MnBi_4Te_7}$ and $\bf{MnBi_6Te_{10}}$. https://doi.org/10.1038/s41467-022-35184-7

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