Planar Hall driven torque in a FM/NM/FM system

Abstract

Electrical manipulation of magnetization is an intensely studied topic with goals of producing energy efficient nanodevices. The charge to spin current conversion in bilayers of magnetic and nonmagnetic materials is one area of investigation. 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. In a sample based on CoNi/Au/CoFeB, spin torque ferromagnetic resonance is used to measure the damping-like torque on the CoFeB layer. The response as a function of the applied field angle and current is consistent with the symmetry expected for a torques produced by the planar Hall effect. We find the strength of this effect to be comparable to that of the spin Hall effect. However, unlike the spin Hall effect, it 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.