  Exploring exotic interface magnetism due to charge transfer and strong
spin-orbit coupling has profound application in future development of
spintronic memory. Here, the emergence, tuning and interpretation of hump-shape
Hall Effect from a CaMnO3/CaIrO3/CaMnO3 trilayer structure are studied in
detail. The hump signal can be recognized as Topological Hall Effect suggesting
the presence of Skyrmion-like magnetic bubbles; but the debated alternative
interpretation where the signal being an artefact between two cancelling
Anomalous Hall Effect loops is also discussed. Firstly, by tilting the magnetic
field direction, the evolution of Hall signal suggests transformation of the
bubbles topology into a more trivial kind. Secondly, by varying the thickness
of CaMnO3, the optimal thicknesses for the hump signal emergence are found,
suggesting a tuning of charge transfer fraction. Using high-resolution
transmission electron microscopy, a stacking fault is also identified, which
distinguishes the top and bottom CaMnO3/CaIrO3 interfaces in terms of charge
transfer fraction and possible interfacial Dzyaloshinskii-Moriya Interaction.
Finally, a spin-transfer torque experiment revealed a low threshold current
density of ~10^9 A/m^2 for initiating the motion of bubbles. This discovery
opens a possible route for integrating Skyrmions with antiferromagnetic
spintronics.
