  Electron transport coupled with magnetism has attracted attention over the
years as exemplified in anomalous Hall effect due to a Berry phase in momentum
space. Another type of unconventional Hall effect -- topological Hall effect,
originating from the real-space Berry phase, has recently become of great
importance in the context of magnetic skyrmions. We have observed topological
Hall effect in bilayers consisting of ferromagnetic SrRuO$_3$ and paramagnetic
SrIrO$_3$ over a wide region of both temperature and magnetic field. The
topological term rapidly decreases with the thickness of SrRuO$_3$, ending up
with the complete disappearance at 7 unit cells of SrRuO$_3$. Combined with
model calculation, we concluded that the topological Hall effect is driven by
interface Dzyaloshinskii-Moriya interaction, which is caused by both the broken
inversion symmetry and the strong spin-orbit coupling of SrIrO$_3$. Such
interaction is expected to realize the N\'{e}el-type magnetic skyrmion, of
which size is estimated to be $\sim$10 nm from the magnitude of topological
Hall resistivity. The results established that the high-quality oxide interface
enables us to tune the chirality of the system; this can be a step towards the
future topological electronics.
