Exchange-Biased Quantum Anomalous Hall Effect

Peng Zhang; Purnima P Balakrishnan; Christopher Eckberg; Peng Deng; Tomohiro Nozaki; Su Kong Chong; Patrick Quarterman; Megan E Holtz; Brian B Maranville; Gang Qiu; Lei Pan; Eve Emmanouilidou; Ni Ni; Masashi Sahashi; Alexander Grutter; Kang L Wang

doi:10.1002/adma.202300391

Exchange-Biased Quantum Anomalous Hall Effect

Adv Mater. 2023 Aug;35(31):e2300391. doi: 10.1002/adma.202300391. Epub 2023 Jun 27.

Authors

Peng Zhang¹, Purnima P Balakrishnan², Christopher Eckberg^{1

3

4

5}, Peng Deng¹, Tomohiro Nozaki⁶, Su Kong Chong¹, Patrick Quarterman², Megan E Holtz⁷, Brian B Maranville², Gang Qiu¹, Lei Pan¹, Eve Emmanouilidou⁸, Ni Ni⁸, Masashi Sahashi⁶, Alexander Grutter², Kang L Wang^{1

8

9}

Affiliations

¹ Department of Electrical and Computer Engineering, University of California Los Angeles, Los Angeles, CA, 90095, USA.
² NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899-6102, USA.
³ Fibertek Inc., Herndon, VA, 20171, USA.
⁴ US Army Research Laboratory, Adelphi, MD, 20783, USA.
⁵ US Army Research Laboratory, Playa Vista, CA, 90094, USA.
⁶ Department of Electronic Engineering, Tohoku University, Sendai, 980-8579, Japan.
⁷ Material Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland, 20899, USA.
⁸ Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA, 90095, USA.
⁹ Department of Materials Science and Engineering, University of California, Los Angeles, CA, 90095, USA.

PMID: 37207689
DOI: 10.1002/adma.202300391

Abstract

The quantum anomalous Hall (QAH) effect is characterized by a dissipationless chiral edge state with a quantized Hall resistance at zero magnetic field. Manipulating the QAH state is of great importance in both the understanding of topological quantum physics and the implementation of dissipationless electronics. Here, the QAH effect is realized in the magnetic topological insulator Cr-doped (Bi,Sb)₂ Te₃ (CBST) grown on an uncompensated antiferromagnetic insulator Al-doped Cr₂ O₃ . Through polarized neutron reflectometry (PNR), a strong exchange coupling is found between CBST and Al-Cr₂ O₃ surface spins fixing interfacial magnetic moments perpendicular to the film plane. The interfacial coupling results in an exchange-biased QAH effect. This study further demonstrates that the magnitude and sign of the exchange bias can be effectively controlled using a field training process to set the magnetization of the Al-Cr₂ O₃ layer. It demonstrates the use of the exchange bias effect to effectively manipulate the QAH state, opening new possibilities in QAH-based spintronics.

Keywords: antiferromagnet; exchange bias; quantum anomalous Hall; topological insulators.

Abstract

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