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)]4multilayers, 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 1×107A/cm2. The damping-like SOT efficiency ξDLwas extracted from an extended harmonic Hall measurement. We demonstrated that the ξDLcan be effectively modulated by tPt/tNiratio 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.