Enhanced spin-orbit torque efficiency with low resistivity in perpendicularly magnetized heterostructures consisting of Si-alloyed β-W layers

Abstract

Spin-orbit torque (SOT) based magnetization switching is of current technological interest to demonstrate its utilization in nonvolatile embedded memory and logic devices. These devices require perpendicular magnetic anisotropy (PMA) for high bit density, significant SOT efficiency to warrant low power consumption, and external field-free magnetization switching. Above all, materials associated with these devices must be semiconductor fabrication friendly. However, only a few materials and their heterostructures previously explored fulfill the requirements. Here, we propose a W-Si alloy, a widely used material in semiconductor devices, as the spin current-generating layer. First, we investigate the spin Hall conductivity of W-Si alloys by adding Si atoms to the β-W matrix using the first-principles calculations. Then, experimentally, we confirm that the heterostructure consisting of W-Si (4 at%)/CoFeB exhibits PMA, a high damping-like SOT efficiency (∼0.58), and low longitudinal resistivity (∼135 μΩ cm). Furthermore, we estimate ten times smaller write power consumption than the heterostructure based on the pristine β-W. The proposed W-Si/CoFeB heterostructures can withstand post-deposition heat treatment up to 500 °C.