Damping and Interfacial Dzyaloshinskii-Moriya Interaction in Thulium Iron Garnet/Bismuth-Substituted Yttrium Iron Garnet Bilayers

Thin films of ferrimagnetic iron garnets can exhibit useful magnetic properties, including perpendicular magnetic anisotropy (PMA) and high domain wall velocities. In particular, bismuth-substituted yttrium iron garnet (BiYIG) films grown on garnet substrates have a low Gilbert damping but zero Dzyaloshinskii-Moriya interaction (DMI), whereas thulium iron garnet (TmIG) films have higher damping but a nonzero DMI. We report the damping and DMI of thulium-substituted BiYIG (BiYTmIG) and TmIG|BiYIG bilayer thin films deposited on (111) substituted gadolinium gallium garnet and neodymium gallium garnet (NGG) substrates. The films are epitaxial and exhibit PMA. BiYIG|TmIG bilayers have a damping value that is an order of magnitude lower than that of TmIG, and BiYIG|TmIG|NGG have DMI of 0.0145 ± 0.0011 mJ/m², similar to that of TmIG|NGG. The bilayer therefore provides a combination of DMI and moderate damping, useful for the development of high-speed spin orbit torque-driven devices.