Gate Control of Spin–Orbit Torque in a Sputtered Bi₂Se₃/Ni₈₁Fe₁₉ Device

Abstract

Sputtered Bi2Se3 has 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/Ni81Fe19 device, 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.