Dual SOT Switching Modes in a Single Device Geometry for Neuromorphic Computing

Neuromorphic computing aims to replicate the brain's efficient processing through artificial neurons and synapses, requiring binary and multilevel switching. We present a PtMn/(Co/Pd)₄/Ta device that uniquely enables dual spin-orbit torque (SOT) switching modes─binary and multilevel (analog)─within the same geometry and stack structure, eliminating the need for device modifications. Binary SOT switching is achieved via domain wall nucleation and propagation at moderate current levels (∼65 mA), while multilevel switching occurs via domain nucleation mode without significant propagation after a high-current treatment (∼85 mA). The transition between two modes originates from structural changes after the current treatment. These modes allow for neuronal and synaptic functionalities, with the device achieving 96% accuracy in digit/letter recognition on the MNIST data set using an artificial neural network (ANN). The device's robust perpendicular magnetic anisotropy (PMA), dual-mode switching under a small in-plane field (<i>H</i>_X), and simplified fabrication underscore its promise as an energy-efficient solution for neuromorphic computing.