Shape anisotropy induced field-free switching and enhancement of dampinglike field in Pt/Co/PtMn heterostructures with a wedged ultrathin antiferromagnetic PtMn layer

Current-induced spin-orbit torque (SOT) switching of perpendicular magnetization requires an additional symmetry breaking, calling for modifications of the conventional SOT devices. Here, we have systematically investigated current-induced magnetization switching and dampinglike field in Pt/Co/PtMn trilayer films with a wedged ultrathin antiferromagnetic (AFM) PtMn layer. The symmetry is broken by the effective shape anisotropy in the wedged ultrathin AFM PtMn layer, resulting in the observed field-free SOT switching. Quantitative characterization manifests that the dampinglike (DL) field is boosted up to 30% through wedging the AFM PtMn layer. Additional experiments with in situ magnetic field and micromagnetic simulations indicate the canting of spins caused by the wedge shape accounts for the observed field-free switching and enhancement of SOT efficiency. Our findings provide an easier approach to field-free switching and HDL enhancing for magnetic memory devices with high density and low power consumption.