Deterministic magnetic switching of perpendicular magnets by gradient current density

We investigated the current-induced magnetization switching in a perpendicular magnetized Pt/CoNiCo/Pt sandwich structure by spin-orbit torques under in-plane gradient current density. The gradient spin current density resulted from the spin Hall effect along the current direction was achieved by designing a bottom wedged Pt electrode. An in-plane effective field along the current direction is induced by the wedged Pt layer, which determines the direction of the current induced magnetization switching. The effective field increased with the slope of the wedged Pt, and is sufficient to induce deterministic switching of nearly 90% domains with the slope value of 0.21.