Our laboratory collaborated with Professor Raynien Kwo in National Tsing Hua University and Professor Minghwei Hong in National Taiwan University to study the interaction between the topological surface state and the ambient system in the high-quality three-dimensional topological insulator/ferrimagnetic insulator bilayer structure. The result of ferromagnetic resonance experiment proves that the strong interface coupling exhibits in-plane magnetic anisotropy and enhances resonance damping properties. The Curie temperature of the magnetic proximity effect is 180K. It exhibits in-plane magnetic anisotropy in the high temperature and perpendicular magnetic anisotropy in the low temperature. The effect of effective magnetic field enhancement, resulted from exchange coupling, is also observed at low temperature. It clearly demonstrates the influence of surface states on the dynamic behavior of magnetic moments. This research paper was published on January 15, 2018 in NATURE COMMUNICATIONS.

We use numerical simulation to study the transfer of spin waves in microscopic waveguides and the interaction with magnetic domain walls. We found a high anisotropy between the dynamic behavior of the magnetic domain walls, the correlation between the parameters, and the penetration of the spin wave.