Spin-orbit torque in perpendicularly magnetized [Pt/Ni] multilayers

The performance of spin-orbit torque (SOT) in heavy metal/ferromagnetic metal periodic multilayers has attracted widespread attention. In this paper, we have successfully fabricated a series of perpendicular magnetized [Pt(2-t)/Ni(t)]₄ multilayers, and studied the SOT in the multilayers by varying the thickness of Ni layer t. The current induced magnetization switching was achieved with a critical current density of 1 × 10⁷ A/cm². The damping-like SOT efficiency ξ _DL was extracted from an extended harmonic Hall measurement. We demonstrated that the ξ _DL can be effectively modulated by t _Pt/t _Ni ratio of Pt and Ni in the multilayers. The SOT investigation about the [Pt/Ni] _N multilayers might provide new material candidates for practical perpendicular SOT-MRAM devices.