Annealing Temperature Effects on Spin Hall Magnetoresistance in Perpendicularly Magnetized W/CoFeB Bilayers

In this paper, we studied the annealing temperature effects on the spin Hall magnetoresistance (SMR) in W/CoFeB metallic bilayer systems. The bilayers were deposited using dc magnetron sputtering. The angle-dependent magnetoresistance was performed in a field of 8 T. The sample was rotated in the yz plane to isolate the SMR signal from the anisotropic magnetoresistance present in metallic systems. For annealing temperatures above 350 °C, we found the SMR signal reduces with an increase in annealing temperature. By measuring the SMR for samples with a varying W layer thickness we were able to find that the spin Hall angle decreases as annealing temperature increases and the spin diffusion length for W remains almost constant with annealing temperature.