  Charged particles exhibit the Hall effect in the presence of magnetic fields.
Analogously, ferromagnetic skyrmions with non-zero topological charges and
finite fictitious magnetic fields exhibit the skyrmion Hall effect, which is
detrimental for applications. The skyrmion Hall effect has been theoretically
predicted to vanish for antiferromagnetic skyrmions because the fictitious
magnetic field, proportional to net spin density, is zero. We experimentally
confirm this prediction by observing current-driven transverse elongation of
pinned ferrimagnetic bubbles. Remarkably, the skyrmion Hall effect, estimated
with the angle between the current and bubble elongation directions, vanishes
at the angular momentum compensation temperature where the net spin density
vanishes. This study establishes a direct connection between the fictitious
magnetic field and spin density, offering a pathway towards the realization of
skyrmionic devices.
