Room-temperature high spin-orbit torque due to quantum confinement in sputtered Bi x Se (1-x) films

• Published in: Nature materials Vol. 17; no. 9; pp. 800 - 807
• Main Authors: Dc, Mahendra, Grassi, Roberto, Chen, Jun-Yang, Jamali, Mahdi, Reifsnyder Hickey, Danielle, Zhang, Delin, Zhao, Zhengyang, Li, Hongshi, Quarterman, P, Lv, Yang, Li, Mo, Manchon, Aurelien, Mkhoyan, K Andre, Low, Tony, Wang, Jian-Ping
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 01.09.2018
• Subjects: Charge efficiency; Computer simulation; Direct current; Efficiency; Engineering; Ferromagnetic resonance; Ferromagnetism; Generators; Heterostructures; Magnetic fields; Magnetic switching; Memory devices; Microscopy; Molecular beam epitaxy; Multilayers; Quantum confinement; Quantum transport; Room temperature; Silicon substrates; Spin-orbit interactions; Standard deviation; Thin films; Torque
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/s41563-018-0136-z

The spin-orbit torque (SOT) that arises from materials with large spin-orbit coupling promises a path for ultralow power and fast magnetic-based storage and computational devices. We investigated the SOT from magnetron-sputtered Bi Se thin films in Bi Se /Co Fe B heterostructures by using d.c. planar Hall and spin-torque ferromagnetic resonance (ST-FMR) methods. Remarkably, the spin torque efficiency (θ ) was determined to be as large as 18.62 ± 0.13 and 8.67 ± 1.08 using the d.c. planar Hall and ST-FMR methods, respectively. Moreover, switching of the perpendicular CoFeB multilayers using the SOT from the Bi Se was observed at room temperature with a low critical magnetization switching current density of 4.3 × 10  A cm . Quantum transport simulations using a realistic sp tight-binding model suggests that the high SOT in sputtered Bi Se is due to the quantum confinement effect with a charge-to-spin conversion efficiency that enhances with reduced size and dimensionality. The demonstrated θ , ease of growth of the films on a silicon substrate and successful growth and switching of perpendicular CoFeB multilayers on Bi Se films provide an avenue for the use of Bi Se as a spin density generator in SOT-based memory and logic devices.