Spin Hall effect mediated current-induced deterministic switching in all-metallic perpendicularly magnetized Pt/Co/Pt trilayers

A magnetic field free current-induced deterministic switching is demonstrated in a perpendicularly magnetized all-metallic Pt/Co/Pt thin film system with a small tilt in anisotropy axis. We realized this in devices where the ultrathin Co layer was grown using an oblique angle sputter deposition technique that had resulted in a small tilt of magnetic anisotropy from the film normal. By performing out-of-plane magnetization hysteresis measurements under bias magnetic field applied along various in-plane directions the tilt angle was estimated to be around 3.3 degrees (+/- 0.3 degrees). A deterministic current-induced magnetization switching could be achieved when the in-plane current was applied perpendicular to the anisotropy tilt axis, but the switching was stochastic when the current was applied in the direction of the tilt (in the tilt plane). By preparing Pt/Co/Pt stacks with unequal top and bottom Pt thickness, sufficient spin-orbit torque (SOT) could be applied to switch the magnetization of the Co layer at current densities as low as 1.5 x 10(7) A/cm(2). The switching phase diagram (SPD) constructed by plotting the critical current density versus applied in-plane magnetic field (HIB x) confirms spin Hall effect based SOT mechanism to be responsible for the magnetization switching. The asymmetry observed in the SPD (about H-x(IB) = 0) is in agreement with the macrospin simulations and it suggests that the tilt in the magnetic anisotropy from the film normal makes the switching deterministic even without an in-plane magnetic field bias