  The advent of ferromagnetism in two-dimensional (2D) van der Waals (vdW)
magnets has stimulated high interest in exploring topological magnetic
textures, such as skyrmions for use in future skyrmion-based spintronic
devices. To engineer skyrmions in vdW magnets by transforming Bloch-type
magnetic bubbles into N\'eel-type skyrmions, the heterostructure of heavy
metal/vdW magnetic thin film has been made to induce interfacial
Dzyaloshinskii-Moriya interaction (DMI). However, the unambiguous
identification of the magnetic textures inherent to vdW magnets, e.g., whether
the magnetic twists (skyrmions/domain walls) are N\'eel- or Bloch-type, is
unclear. Here we demonstrate that the N\'eel- or Bloch-type magnetic twists can
be tuned in the vdW magnet Fe3GeTe2 (FGT) with/without interfacial DMI. We use
an in-plane magnetic field to align the modulation wavevector q of the
magnetizations in order to distinguish the N\'eel- or Bloch-type magnetic
twists. We observe that q is perpendicular to the in-plane field in the
heterostructure (Pt/oxidized-FGT/FGT/oxidized-FGT), while q aligns at a rotated
angle with respect to the field direction in the thin plate by thinning bulk
FGT. We find that the aligned domain wall twists hold fan-like modulations,
coinciding qualitatively with our computational results.
