Large Field-Like Orbital Torque in FeNi/Cr Heterostructures

Orbital torque is one of the potential approaches to achieve current-driven magnetization switching in next-generation spintronic devices, where the field-like orbital torque plays a critical role to obtain field-free magnetization switching. Here, we report a large field-like orbital torque observed in FeNi/Cr heterostructures by the symmetric components of the spin-torque ferromagnetic resonance signals, which induced a sin2θ symmetry in the angular dependence of the symmetric component amplitudes. This field-like orbital torque is along the m × z direction, with an efficiency (−0.033) comparable to that of the damping-like torque (0.068). A significant tilting of the orbital current polarization generated by the orbital Hall effect in the Cr layer leads to the z-component of the orbital current polarization and the large field-like orbital torque. Furthermore, the y-component of the orbital current polarization shows a reversal behavior as the Cr thickness decreases, demonstrating the competition between the orbital currents generated by the surface oxide layer and those within the Cr bulk. These findings provide insights into the orbital torques in the 3d transition metals and highlight the potential of orbital-torque-driven magnetization switching in the absence of external magnetic fields for the applications of spintronic devices.