  The integration of quantum materials like topological insulators (TIs) with
magnetic insulators (MIs) has important technological implications for
spintronics and quantum computing. Here we report excellent crystallinity of
c-axis oriented epitaxial TI films Bi2Se3 grown on MI films, a rare earth iron
garnet (ReIG), such as thulium iron garnet (Tm3Fe5O12, TmIG) by molecular beam
epitaxy (MBE) with a Se-buffered low-temperature (SBLT) growth technique. We
demonstrated a streaky reflection high-energy electron diffraction pattern
starting from the very first quintuple layer of Bi2Se3, indicating the
high-quality interface between TmIG and Bi2Se3, a prerequisite for studying
interfacial exchange coupling effects. The strong interfacial exchange
interaction was manifested by observations of anomalous Hall effect in the
Bi2Se3/TmIG bilayer and a shift of ferromagnetic resonance field of TmIG
induced by Bi2Se3. We have reproducibly grown high-quality Bi2Se3/ReIG and
interfaces using this new TI growth method, which may be applied to grow other
types of van der Waals (vdW) hetero-structures.
