Planar Hall Torque

Ilya Krivorotov, University of California at Irvine

Spin-orbit torques (SOTs) in bilayers of ferromagnetic (FM) and nonmagnetic (NM) materials, such as spin Hall [1] and Rashba [2, 3] torques, enable energy efficient manipulation of magnetization by electric currents. In this talk, I will discuss the discovery [4] of a damping-like SOT arising from planar Hall current in FM conductors [5, 6]. The magnitude of this planar Hall torque (PHT) is similar to that of the giant spin Hall torque in FM/Pt bilayers and strong PHT can be present in a system with negligibly small spin Hall torque such as FM/Au bilayers. We also show that PHT is large enough to cancel magnetic damping of the FM and excite auto-oscillations of the FM magnetization. The discovery of PHT expands the class of materials and systems for energy efficient manipulation of magnetization by giant SOTs.

1. Liu L. et al. (2012) Spin-torque switching with the giant spin Hall effect of tantalum. Science. 336, 555.
2. Miron I. M. et al. (2011) Perpendicular switching of a single ferromagnetic layer induced by in-plane current injection. Nature 476, 189.
3. Kurebayashi H. et al. (2014) An antidamping spin–orbit torque originating from the Berry curvature, Nature Nanotech. 9, 211.
4. Safranski C., Montoya E.A., Krivorotov I.N. (2019) Spin–orbit torque driven by a planar Hall current. Nat. Nanotech. 14, 27.
5. Taniguchi T., Grollier J., Stiles M.D. (2015) Spin-Transfer Torques Generated by the Anomalous Hall Effect and Anisotropic Magnetoresistance. Phys. Rev. Appl. 3, 1.
6. Ochoa H., Zarzuela R., Tserkovnyak Y. (2021) Self-induced spin-orbit torques in metallic ferromagnets, J. Magn. Magn. Mater. 538, 168262.

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PDF file of the talk available here