Field-Free Spin-Orbit Torque Switching of Perpendicular Magnetization by the Rashba Interface

Baoshan Cui; Hao Wu; Dong Li; Seyed Armin Razavi; Di Wu; Kin L Wong; Meixia Chang; Meizhen Gao; Yalu Zuo; Li Xi; Kang L Wang

doi:10.1021/acsami.9b13622

Field-Free Spin-Orbit Torque Switching of Perpendicular Magnetization by the Rashba Interface

ACS Appl Mater Interfaces. 2019 Oct 23;11(42):39369-39375. doi: 10.1021/acsami.9b13622. Epub 2019 Oct 11.

Authors

Baoshan Cui^{1

2}, Hao Wu¹, Dong Li³, Seyed Armin Razavi¹, Di Wu¹, Kin L Wong¹, Meixia Chang², Meizhen Gao², Yalu Zuo², Li Xi², Kang L Wang¹

Affiliations

¹ Department of Electrical and Computer Engineering , University of California , Los Angeles , California 90095 , United States.
² Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education & School of Physical Science and Technology , Lanzhou University , Lanzhou 730000 , P. R. China.
³ Research Institute of Materials Science , Shanxi Normal University , Linfen 041004 , P. R. China.

PMID: 31603641
DOI: 10.1021/acsami.9b13622

Abstract

Current-induced spin-orbit torques (SOTs) enable efficient electrical manipulation of the magnetization in heterostructures with a perpendicular magnetic anisotropy through the Rashba effect or spin-Hall effect. However, in conventional SOT-based heterostructures, an in-plane bias magnetic field along the current direction is required for the deterministic switching. Here, we report that the field-free SOT switching can be achieved by introducing a wedged oxide interface between a heavy metal and a ferromagnet. The results demonstrate that the field-free SOT switching is determined by a current-induced perpendicular effective field (H_z^eff) originating from the interfacial Rashba effect due to the lateral structural symmetry-breaking introduced by the wedged oxide layer. Furthermore, we show that the sign and magnitude of H_z^eff exhibit a significant dependence on the interfacial oxygen content, which can be controlled by the inserted oxide thickness. Our findings provide a deeper insight into the field-free SOT switching by the interfacial Rashba effect.

Keywords: Rashba effect; field-free magnetization switching; interfacial decoration; interfacial oxygen content; perpendicular magnetic anisotropy; spin−orbit torque.