Tailoring exchange couplings in magnetic topological-insulator/antiferromagnet heterostructures

Abstract

Magnetic topological insulators such as Cr-doped (Bi,Sb)2Te3 provide a platform for the realization of versatile time-reversal symmetry-breaking physics. By constructing heterostructures exhibiting Néel order in an antiferromagnetic CrSb and ferromagnetic order in Cr-doped (Bi,Sb)2Te3, we realize emergent interfacial magnetic phenomena which can be tailored through artificial structural engineering. Through deliberate geometrical design of heterostructures and superlattices, we demonstrate the use of antiferromagnetic exchange coupling in manipulating the magnetic properties of magnetic topological insulators. Proximity effects are shown to induce an interfacial spin texture modulation and establish an effective long-range exchange coupling mediated by antiferromagnetism, which significantly enhances the magnetic ordering temperature in the superlattice. This work provides a new framework on integrating topological insulators with antiferromagnetic materials and unveils new avenues towards dissipationless topological antiferromagnetic spintronics.

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Figure 1: Exchange couplings of Dirac fermions and AFM for different heterostructures.
Figure 2: Novel magnetic interplays in MTI/AFM superlattices (SLs).
Figure 3: Capturing the spin textures in the SL and trilayer by neutron techniques.
Figure 4: Observation of giant enhancements in exchange field (HEX), Curie temperature (TC), and coercive field (HC) in the superlattices.

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Acknowledgements

We thank S. Watson, R. Erwin and W. Chen for their assistance in the neutron diffraction experiment. We are also grateful for the support from the Army Research Office accomplished under Grant Number W911NF-15-1-10561. We also acknowledge the support by the Spins and Heat in Nanoscale Electronic Systems (SHINES), an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under award #SC0012670, and the National Science Foundation (DMR-1411085). This work was supported in part by the FAME Center, one of six centres of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA. Certain commercial equipment, instruments, or materials are identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.

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Q.L.H., X.K. and K.L.W. conceived and designed the experiments. Q.L.H., L.P., X.C. and K.M. performed the sample growth and device fabrication. B.Z. and X.H. carried out the TEM experiments. All the authors contributed to the measurements and analyses. A.J.G., S.M.D., B.J.K., W.R.II and J.A.B. performed the neutron experiments and analyses. Q.L.H., X.K., A.J.G., G.Yin and K.L.W. wrote the manuscript with contributions from all the authors.

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Correspondence to Qing Lin He or Kang L. Wang.

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The authors declare no competing financial interests.

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He, Q., Kou, X., Grutter, A. et al. Tailoring exchange couplings in magnetic topological-insulator/antiferromagnet heterostructures. Nature Mater 16, 94–100 (2017). https://doi.org/10.1038/nmat4783

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