Magnetization switching using topological surface states

Peng Li; James Kally; Steven S-L Zhang; Timothy Pillsbury; Jinjun Ding; Gyorgy Csaba; Junjia Ding; J S Jiang; Yunzhi Liu; Robert Sinclair; Chong Bi; August DeMann; Gaurab Rimal; Wei Zhang; Stuart B Field; Jinke Tang; Weigang Wang; Olle G Heinonen; Valentine Novosad; Axel Hoffmann; Nitin Samarth; Mingzhong Wu

doi:10.1126/sciadv.aaw3415

Magnetization switching using topological surface states

Sci Adv. 2019 Aug 30;5(8):eaaw3415. doi: 10.1126/sciadv.aaw3415. eCollection 2019 Aug.

Authors

Peng Li¹, James Kally², Steven S-L Zhang³, Timothy Pillsbury², Jinjun Ding¹, Gyorgy Csaba⁴, Junjia Ding³, J S Jiang³, Yunzhi Liu⁵, Robert Sinclair⁵, Chong Bi⁶, August DeMann¹, Gaurab Rimal⁷, Wei Zhang^{8

3}, Stuart B Field¹, Jinke Tang⁷, Weigang Wang⁶, Olle G Heinonen³, Valentine Novosad³, Axel Hoffmann³, Nitin Samarth², Mingzhong Wu¹

Affiliations

¹ Department of Physics, Colorado State University, Fort Collins, CO 80523, USA.
² Department of Physics, Pennsylvania State University, University Park, PA 16802, USA.
³ Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA.
⁴ Faculty of Information Technology and Bionics, Pazmany Peter Catholic University, Budapest, Hungary.
⁵ Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA.
⁶ Department of Physics, University of Arizona, Tucson, AZ 85721, USA.
⁷ Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071, USA.
⁸ Department of Physics, Oakland University, Rochester, MI 48309, USA.

Abstract

Topological surface states (TSSs) in a topological insulator are expected to be able to produce a spin-orbit torque that can switch a neighboring ferromagnet. This effect may be absent if the ferromagnet is conductive because it can completely suppress the TSSs, but it should be present if the ferromagnet is insulating. This study reports TSS-induced switching in a bilayer consisting of a topological insulator Bi₂Se₃ and an insulating ferromagnet BaFe₁₂O₁₉. A charge current in Bi₂Se₃ can switch the magnetization in BaFe₁₂O₁₉ up and down. When the magnetization is switched by a field, a current in Bi₂Se₃ can reduce the switching field by ~4000 Oe. The switching efficiency at 3 K is 300 times higher than at room temperature; it is ~30 times higher than in Pt/BaFe₁₂O₁₉. These strong effects originate from the presence of more pronounced TSSs at low temperatures due to enhanced surface conductivity and reduced bulk conductivity.