  Electrical detection of topological magnetic textures such as skyrmions is
currently limited to conducting materials. While magnetic insulators offer key
advantages for skyrmion technologies with high speed and low loss, they have
not yet been explored electrically. Here, we report a prominent topological
Hall effect in Pt/Tm$_3$Fe$_5$O$_{12}$ bilayers, where the pristine
Tm$_3$Fe$_5$O$_{12}$ epitaxial films down to 1.25 unit cell thickness allow for
tuning of topological Hall stability over a broad range from 200 to 465 K
through atomic-scale thickness control. Although Tm$_3$Fe$_5$O$_{12}$ is
insulating, we demonstrate the detection of topological magnetic textures
through a novel phenomenon: 'spin-Hall topological Hall effect' (SH-THE), where
the interfacial spin-orbit torques allow spin-Hall-effect generated spins in Pt
to experience the unique topology of the underlying skyrmions in
Tm$_3$Fe$_5$O$_{12}$. This novel electrical detection phenomenon paves a new
path for utilizing a large family of magnetic insulators in future skyrmion
technologies.
