Increase in spin-Hall effect and influence of anomalous Nernst effect on spin-Hall magnetoresistance in β-phase and α-phase W_100-xTa_x/CoFeB systems

We studied the spin-Hall effect in W_100-xTa_x with various Ta compositions for W-Ta alloy/CoFeB/MgO heterostructures by means of spin-Hall magnetoresistance (SMR). We synthesized W-Ta alloys with both α-phase and β-phase by controlling the sputtering condition. We found that, in both α-phase and β-phase W-Ta alloys, the amplitude in SMR signals increases by alloying W with Ta at certain x. The analysis based on the drift-diffusion model reveals that the increase in SMR originates from an enhancement of the spin-Hall angles θ _SH. Moreover, we observed the influence of anomalous Nernst effect on SMR for the high-resistive W-Ta/CoFeB systems.