Enhancement of the Spin-Mixing Conductance in Co -Fe -B /W Bilayers by Interface Engineering

Efficient generation of spin current in ferromagnet/heavy-metal systems is critical to spin orbitronics, but the interface limits the efficiency of transmitting spin current, and weakens the effective spin Hall angle of the heavy-metal layer. In this study the authors enhance the spin-mixing conductance in such a multilayer by inserting an atomically thin layer of $\ensuremath{\alpha}$-W at the interface, and propose a corresponding model that considers the spin-backflow current. This approach is expected to further reduce the charge-current density and realize power-efficient spin-orbit-torque devices based on the important Co-Fe-B/W system.