The effect of spin pumping in epitaxial Bi2Se3 films

Bi₂Se₃ is one of the promising topological insulator (TI) materials, which have both helical spin polarization and strong spin-orbit coupling (SOC). In this work, high quality Bi₂Se₃ thin films were grown on c-plane sapphire (Al₂O₃) substrates by molecular beam epitaxy (MBE). The central part of the Bi₂Se₃ layer was covered with a permalloy (Ni₈₀Fe₂₀) layer by ion-beam sputtering (IBS) with a shadow mask. The inverse spin Hall effect (ISHE) of Bi₂Se₃/Py bilayers have been observed by spin pumping method at room temperature (RT). The magnitude of the electric voltage is proportional to the microwave excitation power and the direction of voltage is reversed when the direction of external magnetic field is reversed, proving that the voltage is due to ISHE induced by the spin pumping. Moreover, when the thickness of Bi₂Se₃ is equal to 8nm, the ISHE voltage has the maximum, evaluating the spin-diffusion length of Bi₂Se₃ is about 8nm.