  Engineering of magnetic heterostructures for spintronic applications has
entered a new phase, driven by the recent discoveries of topological materials
and exfoliated van der Waals materials. Their low-dimensional properties can be
dramatically modulated in designer heterostructures via proximity effects from
adjacent materials, thus enabling the realization of diverse quantum states and
functionalities. Here we investigate spin-orbit coupling (SOC) proximity
effects of Pt on the recently discovered quasi-two-dimensional ferromagnetic
state at FeSi surface. Skyrmionic bubbles (SkBs) are formed as a result of the
enhanced interfacial Dzyloshinskii-Moriya interaction. The strong pinning
effects on the SkBs are evidenced from the significant dispersion in size and
shape of the SkBs and are further identified as a greatly enhanced threshold
current density required for depinning of the SkBs. The robust integrity of the
SkB assembly leads to the emergence of higher-order nonlinear Hall effects in
the high current density regime, which originate from nontrivial Hall effects
due to the noncollinearity of the spin texture, as well as from the
current-induced magnetization dynamics via the augmented spin-orbit torque.
