Anisotropic Spin-orbit Torque Generation in Epitaxial SrIrO₃ by Symmetry Design

Authors

T. Nan, University of Wisconsin-Madison
T. J. Anderson, University of Wisconsin-Madison
J. Gibbons, Cornell University
K. Hwang, University of Toronto
Neil Campbell, University of Wisconsin-Madison
H. Zhou, Argonne National Laboratory
Y. Q. Dong, Argonne National Laboratory
G. Y. Kim, Pohang University of Science and Technology
Ding-Fu Shao, University of Nebraska-LincolnFollow
Tula R. Paudel, University of Nebraska-LincolnFollow
N. Reynolds, Cornell University
X. J. Wang, Northeastern University
N. X. Sun, Northeastern University
Evgeny Y. Tsymbal, University of Nebraska-LincolnFollow
Si-Young Choi, Pohang University of Science and Technology
M. S. Rzchowski, University of Wisconsin-Madison
Yong Baek Kim, Korea Institute for Advanced Study
D. C. Ralph, Cornell University
Chang-Beom Eom, University of Wisconsin-MadisonFollow

ORCID IDs

Tsymbal http://orcid.org/0000-0002-6728-5481

Paudel https://orcid.org/0000-0002-9952-9435

Document Type

Article

Date of this Version

8-13-2019

Citation

Proceedings of the National Academy of Sciences (August 13, 2019) 116: 16,186-16,191

doi: 10.1073/pnas.1812822116

Edited by Qi Li, Pennsylvania State University, and accepted by Editorial Board Member Tobin J. Marks

Supplemental material is available at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1812822116/-/DCSupplemental

Comments

Copyright 2019, National Academy of Sciences. Used by permission

License: PNAS license

Abstract

Spin-orbit coupling (SOC), the interaction between the electron spin and the orbital angular momentum, can unlock rich phenomena at interfaces, in particular interconverting spin and charge currents. Conventional heavy metals have been extensively explored due to their strong SOC of conduction electrons. However, spin-orbit effects in classes of materials such as epitaxial 5d-electron transition-metal complex oxides, which also host strong SOC, remain largely unreported. In addition to strong SOC, these complex oxides can also provide the additional tuning knob of epitaxy to control the electronic structure and the engineering of spin-to-charge conversion by crystalline symmetry. Here, we demonstrate room-temperature generation of spin-orbit torque on a ferromagnet with extremely high efficiency via the spin-Hall effect in epitaxial metastable perovskite SrIrO₃.We first predict a large intrinsic spin-Hall conductivity in orthorhombic bulk SrIrO₃ arising from the Berry curvature in the electronic band structure. By manipulating the intricate interplay between SOC and crystalline symmetry, we control the spin-Hall torque ratio by engineering the tilt of the corner-sharing oxygen octahedra in perovskite SrIrO₃ through epitaxial strain. This allows the presence of an anisotropic spin-Hall effect due to a characteristic structural anisotropy in SrIrO₃ with orthorhombic symmetry. Our experimental findings demonstrate the heteroepitaxial symmetry design approach to engineer spin-orbit effects. We therefore anticipate that these epitaxial 5d transition-metal oxide thin films can be an ideal building block for low-power spintronics.