Probing the Spin Hall Characteristics of W/CoFeB/MgO Based Heterostructures for Spin‐Orbit Torque Based Magnetic Random Access Memory Application

Abstract

Abstract In this work, the spin Hall characteristics of W/CoFeB/MgO have been systematically studied to provide an in‐depth insight for the optimization of the SOT‐MRAM channel. The bcc and β phases of tungsten (W) are identified clearly from XRD and resistivity studies, which shows marked impact on the electrical characteristics. Moreover, the same is found have tremendous affect on W's spin Hall characteristics with a twelvefold increase of the spin Hall angle ΘSH. The evaluation of W/CoFeB interfacial spin mixing conductance geff↑↓ using ab initio studies shows good coherency with the same evaluated experimentally, which is used to estimate interfacial spin transparency T to accurately evaluate intrinsic spin Hall conductivity σSH of W. The findings equivocate for a strong claim on β‐W's σSH to be around −0.23 ∓ 0.03, addressing the ongoing discrepancy. Increasing boron concentration in (Co1Fe3)100−xBx and thermal annealing temperature are found to reduce ΘSH effectively which is inferred to boron diffusion toward W. Alloying of W with Ta does not necessarily enhance ΘSH, for which very optimized relative concentration and the alloy growth phase is critical. The findings can significantly contribute to the ongoing SOT‐MRAM development for achieving various means of control for improvement in the device characteristics.

Keywords

• alloy spin Hall
• boron diffusion
• β‐W spin Hall
• interfacial spin transparency
• spin Hall angle