Planar Hall Driven Spin Torque in a Ferromagnet/Nonmagnet/Ferromagnet System

Christopher Safranski, IBM

July 24, 2020

Transport current manipulation of magnetization based on spin-orbit effects aims to produce energy efficient nanomagnet devices. One area of investigation is the charge to spin current conversion in layers of magnetic and nonmagnetic materials. Typically studied materials have been mostly limited to the generation of in-plane polarized spin currents. We investigate spin currents produced by the planar Hall effect in Co/Ni multilayers, which carry a polarization dictated by the FM magnetization direction. We measure damping-like torques in FM/NM/FM systems via spin torque ferromagnetic resonance of patterned structures. The slope of linewidth vs bias current is used to quantify the torques. The angular dependence of this slope is consistent with the symmetry expected for torques produced by the planar Hall effect [1,2]. We find the magnitude of the spin-current thus generated to be comparable to that of the spin Hall effect in materials such as Pt. However, unlike the spin Hall effect, planar Hall can produce a partially out of plane spin polarization. Our results indicate that the planar Hall effect holds potential as a spin current source with a controllable polarization direction.

[1] Phys. Rev. Appl. 3, 044001 (2015).
[2] Nat. Nanotechnol. 14, 27–30 (2019)