Ferromagnetic Resonance and Spin Pumping in Transferred Topological Insulator on Ferrimagnetic Insulator Heterostructures
C. C. Tseng1*, Y. C. Liu1, C. C. Chen1, S. R. Yang1, Y. T. Fanchiang2, C. K. Cheng2, S. F. Lee3, J. G. Lin4, M. Hong2, J. Kwo1
1Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
2Department of Physics, National Taiwan University, Taipei, Taiwan
3Institute of Physics, Academia Sinica, Taipei, Taiwan
4Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
* Presenter:C. C. Tseng
Large spin-to-charge conversion is one of the important traits for topological insulator (TI) based spintronics due to its very large spin-orbit coupling (SOC) and spin-momentum locking in the surface state. Bilayers of TIs and various magnetic insulators such as yttrium iron garnet (YIG) with very low magnetic damping are suitable for investigations of high spin-to-charge conversion efficiency in absence of current shunting. However, obtaining high quality TI films directly grown on YIG is challenging, especially for novel phenomena that demand sharp interfaces. In this work we report thorough characterizations of exfoliated MBE-grown Bi2Se3 films transferred on YIG and Ag/YIG films. We demonstrated that in-plane ordered triangular domains and excellent crystallinity previously attained in MBE growth of Bi2Se3 on sapphire were preserved after the transfer process, as confirmed by atomic force microscopy and X-ray diffraction. Ferromagnetic resonance (FMR) results showed an extra peak was induced by the interfacial exchange coupling in transferred Bi2Se3/YIG. Analysis of the FMR linewidths did not display the substantially enhanced damping constant, as was found in Bi2Se3/YIG by direct film growth. Spin pumping measurement was further employed to study the spin-charge conversion from inverse Rashba-Edelstein effect or inverse spin Hall effect in transferred Bi2Se3/YIG, along with transferred Bi2Se3/Ag/YIG with varying Ag layer thickness. Our transfer technique has circumvented the difficulties of growing high quality Bi2Se3 on various substrates, and may be applied to fabricate a variety of novel TI-based heterostructures for spintronics.

Keywords: topological insulator, magnetic insulator, ferromagnetic resonance, spin pumping