Termination switching of antiferromagnetic proximity effect in topological insulator

Chao-Yao Yang; Lei Pan; Alexander J Grutter; Haiying Wang; Xiaoyu Che; Qing Lin He; Yingying Wu; Dustin A Gilbert; Padraic Shafer; Elke Arenholz; Hao Wu; Gen Yin; Peng Deng; Julie Ann Borchers; William Ratcliff 2nd; Kang L Wang

doi:10.1126/sciadv.aaz8463

Termination switching of antiferromagnetic proximity effect in topological insulator

Sci Adv. 2020 Aug 12;6(33):eaaz8463. doi: 10.1126/sciadv.aaz8463. eCollection 2020 Aug.

Authors

Chao-Yao Yang¹, Lei Pan¹, Alexander J Grutter², Haiying Wang³, Xiaoyu Che¹, Qing Lin He^{1

4}, Yingying Wu¹, Dustin A Gilbert^{2

5}, Padraic Shafer⁶, Elke Arenholz^{6

7}, Hao Wu¹, Gen Yin¹, Peng Deng¹, Julie Ann Borchers², William Ratcliff 2nd^{2

8}, Kang L Wang^{1

9

10}

Affiliations

¹ Department of Electrical and Computer Engineering, University of California, Los Angeles, CA 90095, USA.
² NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6102, USA.
³ College of Physics and Material Science, Henan Normal University, Xinxiang 453007, China.
⁴ International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
⁵ Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA.
⁶ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁷ Cornell High Energy Synchrotron Source, Ithaca, NY 14853, USA.
⁸ Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA.
⁹ Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095, USA.
¹⁰ Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA.

Abstract

This work reports the ferromagnetism of topological insulator, (Bi,Sb)₂Te₃ (BST), with a Curie temperature of approximately 120 K induced by magnetic proximity effect (MPE) of an antiferromagnetic CrSe. The MPE was shown to be highly dependent on the stacking order of the heterostructure, as well as the interface symmetry: Growing CrSe on top of BST results in induced ferromagnetism, while growing BST on CrSe yielded no evidence of an MPE. Cr-termination in the former case leads to double-exchange interactions between Cr³⁺ surface states and Cr²⁺ bulk states. This Cr³⁺-Cr²⁺ exchange stabilizes the ferromagnetic order localized at the interface and magnetically polarizes the BST Sb band. In contrast, Se-termination at the CrSe/BST interface yields no detectable MPE. These results directly confirm the MPE in BST films and provide critical insights into the sensitivity of the surface state.

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