Large Spin-Orbit Torque in a Topological Insulator/Magnetic Oxide Heterostructure

Topological insulators (TIs) hold great promise for spintronic devices due to their large charge-to-spin conversion efficiency. It is demonstrated that a TI can induce a spin-orbit torque and switch a neighboring ferromagnetic metal. However, it is unclear whether this is related to the exotic topological surface state (TSS) because the electrons from the ferromagnetic metal can suppress TSS. This talk discusses experiments that identified bona fide surface state-induced spin-orbit torques in a topological insulator Bi₂Se₃/magnetic oxide insulator BaFe₁₂O₁₉ heterostructure. The large spin-orbit torque was able to switch the magnetization of BaFe₁₂O₁₉ up and down. When the magnetization was switched by a magnetic field, a current in Bi₂Se₃ can reduce the switching field by about 4000 Oe. The switching efficiency at 3 K is 300 times higher than at room temperature; it is about 30 times higher than in a Pt/BaFe₁₂O₁₉ structure. Such strong effects originate from the presence of more pronounced TSS at low temperatures due to enhanced surface conductivity and reduced bulk conductivity.

References:

P. Li, J. Kally, S. S.-L. Zhang, T. Pillsbury, J. Ding, G. Csaba, J. Ding, S. Jiang, Y. Liu, R. Sinclair, C. Bi, A. DeMann, G. Rimal, W. Zhang, S. B. Field, J. Tang, W. Wang, O. G. Heinonen, V. Novosad, A. Hoffmann, N. Samarth, M. Wu, Magnetization switching utilizing topological surface states. Sci. Adv. 5, eaaw3415 (2019).

Bio:

Dr. Peng Li is an Assistant Professor of Electrical and Computer Engineering. He received Ph.D. from Department of Electrical Engineering at the University of Notre Dame in 2014. He was as a postdoctoral fellow at Stanford University (2018-2019) and Colorado State University (2014-2015, 2017-2018), a Senior Research Engineer at Seagate Technology (2015-2016). He has published 30 papers in the field of magnetism and spintronics. He has served as a committee member for major international conferences. He is a senior editorial member of IEEE Magnetics Letters, and a reviewer for journals including Science Advances, Nano Letters, Applied Physics Letters, etc.