Enhanced perpendicular anisotropy and Dzyaloshinskii-Moriya interaction with regulatable spin-orbit torque efficiency in Pt/(Co/Ni) multilayers via interfacial AuCu insertion

Abstract The advancement of spintronic devices has necessitated the balance of interfacial perpendicular magnetic anisotropy (PMA), Dzyaloshinskii-Moriya interaction (DMI) and spin-orbit torque (SOT) efficiency. Here we investigated the effect of a 0.1-0.8 nm AuCu ultrathin insertion layer at the interface between Pt and (Co/Ni) multilayer on the PMA and DMI as well as current induced magnetization switching. It is found that, with a 0.1 nm AuCu insertion layer, both PMA and DMI of Pt/(Co/Ni) film are drastically enhanced by 100%, with a doubled perpendicular coercivity ( H c ) and slightly increased critical current density ( J c ) for SOT driven magnetization switching. The complete results reveal that a very small amount of AuCu addition significantly improves the interfacial PMA and DMI, but the AuCu itself has little contribution to them, with interfacial atomic disorder scattering unfavorable to the SOT efficiency. Furthermore, the value of J c for all samples with PMA varied by a factor of five exhibits a similar linear decrease when the in-plane assistant field is scaled by the effective PMA field ( H k ) of the individual sample, indicative of the important roles of both H c and H k for the domain nucleation/propagation mechanism dominated SOT switching. This work proposes a strategy to balance DMI, and PMA in Pt/(Co/Ni) multilayers and deepens the understanding of the SOT switching.