Gate Control of Spin-Orbit Torque in a Sputtered Bi₂Se₃/Ni₈₁Fe₁₉Device

Sputtered Bi₂Se₃has strong potential for use as a topological insulator in spintronic devices because of its perfect spin polarization and ability to be grown on a large scale. In a Bi₂Se₃/Ni₈₁Fe₁₉device, electric field control of spin-orbit torque is clearly observed using second-harmonic measurements. The gate voltage modulates the Fermi level as well as the channel types (i.e., p- or n-type). The strengths of damping-like and field-like torques induced by current are separately extracted for various gate voltages. We find that only damping-like torque is modulated by the gate electric field, showing its maximum value near the Dirac point. In addition, thermal effects mixed with spin-orbit torques are also resolved on the basis of the magnetic field dependence. This work not only evaluates the magnitudes of spin-orbit torques quantitatively but also demonstrates the gate-controlled damping-like torque in a sputtered topological insulator/ferromagnet bilayer.