Current-Induced Spin-Orbit Torque and Field-Free Switching in Mo-Based Magnetic Heterostructures

Magnetic heterostructureMo/Co-Fe-B/MgO has strong perpendicular magnetic anisotropy and thermal stability. Through current-induced hysteresis loop shift measurements, we show that the damping-like spin-orbit torque (SOT) efficiency of Mo/Co-Fe-B/MgO heterostructures is xi(DL) approximate to -0.003 +/- 0.001 and is fairly independent of the annealing temperature from 300 degrees C to 400 degrees C. Although vertical bar xi(DL)vertical bar is small compared to those from Ta- or W-based heterostructures, reversible current-induced SOT switching of a thermally stable Mo/Co-Fe-B/MgO heterostruture can still be achieved. Furthermore, we observe field-free current-induced switching from a Mo/Co-Fe-B/MgO structure with the Mo layer being wedge-deposited. Our results indicate that even for a weak spin-orbit interaction 4d transition metal such as Mo, it is still possible to generate sufficient spin current for conventional SOT switching and to realize field-free current-induced switching by structural engineering.