Quantifying interface and bulk contributions to spin–orbit torque in magnetic bilayers

• Published in: Nature communications 2014-01, Vol.5 (1), p.3042-3042, Article 3042
• Main Authors: Fan, Xin, Celik, Halise, Wu, Jun, Ni, Chaoying, Lee, Kyung-Jin, Lorenz, Virginia O., Xiao, John Q.
• Format: Article
• Language: English
• Subjects: 639/301/119/997; 639/766/25; 639/766/400/1101; Anisotropy; Electric currents; Electromagnetism; Humanities and Social Sciences; Information storage; Lasers; Materials science; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms4042

Spin–orbit interaction-driven phenomena such as the spin Hall and Rashba effect in ferromagnetic/heavy metal bilayers enables efficient manipulation of the magnetization via electric current. However, the underlying mechanism for the spin–orbit interaction-driven phenomena remains unsettled. Here we develop a sensitive spin–orbit torque magnetometer based on the magneto-optic Kerr effect that measures the spin–orbit torque vectors for cobalt iron boron/platinum bilayers over a wide thickness range. We observe that the Slonczewski-like torque inversely scales with the ferromagnet thickness, and the field-like torque has a threshold effect that appears only when the ferromagnetic layer is thinner than 1 nm. Through a thickness-dependence study with an additional copper insertion layer at the interface, we conclude that the dominant mechanism for the spin–orbit interaction-driven phenomena in this system is the spin Hall effect. However, there is also a distinct interface contribution, which may be because of the Rashba effect. Spin–orbit-driven effects are of great interest for spintronic applications but the underlying mechanisms are challenging to probe. Here, the authors develop a sensitive spin–orbit torque magnetometer to quantify the interface and bulk contributions to the spin–orbit torques in magnetic bilayers.