Spin-orbit torque induced reversible coercivity change in Co/Pd multilayer thin films

• In-situ magneto optic Kerr effect measurement shows reversible coercivity change in Co/Pd multilayer.
• Anomalous Hall effect measurement does not show the coercivity change.
• Spin-Hall effect mediated spin orbit torque is proposed to be the underlying reason.

In this work, we report reversible reduction in coercivity of Co/Pd multilayer thin films under high-density direct current biasing. We carried out in-situ focused magneto optic Kerr effect based hysteresis measurement while the specimen was under DC bias. The experiments show a reversible reduction in coercivity during the application of direct current. We propose this reduction occurs due to the field like spin-orbit torque generated by spin Hall effect. These results are further supported by the anomalous Hall effect measurement, which do not show any change in coercivity. The magneto-optic Kerr measurement probes the surface (penetration depth) whereas anomalous Hall effect is a bulk transport behavior. These complimentary measurements prove that the origin of spin-orbit torques in ferromagnetic metal/ heavy metal multilayer thin films is spin-Hall effect.