  The interfacial Dzyaloshinskii-Moriya interaction (DMI) in multilayers of
heavy metal and ferromagnetic metals enables the stabilization of novel chiral
spin structures such as skyrmions. Magnetic insulators, on the other hand can
exhibit enhanced dynamics and properties such as lower magnetic damping and
therefore it is of interest to combine the properties enabled by interfacial
DMI with insulating systems. Here, we demonstrate the presence of interfacial
DMI in heterostructures that include insulating magnetic layers. We use a
bilayer of perpendicularly magnetized insulating thulium iron garnet (TmIG) and
the heavy metal platinum, and find a surprisingly strong interfacial DMI that,
combined with spin-orbit torque results, in efficient switching. The
interfacial origin is confirmed through thickness dependence measurements of
the DMI, revealing the characteristic 1/thickness dependence with one order of
magnitude longer decay length compared to metallic layers. We combine chiral
spin structures and spin-orbit torques for efficient switching and identify
skyrmions that allow us to establish the GGG/TmIG interface as the origin of
the DMI.
