Interfacial strain-driven manipulation of the topological Hall effect in epitaxial supermalloy thin films

The topological Hall effect is highly significant for spintronics applications. In this work, we demonstrate a notable topological Hall effect in strained supermalloy (NiFeMo) thin films deposited on MgO (100) and Al₂O₃ (0001) substrates. X-ray reciprocal space maps confirm the epitaxial growth of NiFeMo thin films, while stress analysis reveals strain-induced tetragonal distortion. Magnetic force microscopy detects skyrmion-like structures, likely resulting from strain-induced spin texture formation. Magneto-optic Kerr effect measurements show 4-fold magnetic anisotropy in NiFeMo/MgO (100), which exhibits a stronger topological Hall effect than NiFeMo/Al₂O₃ (0001). The strain-induced disruption of centrosymmetry in the films likely triggers Dzyaloshinskii-Moriya (DM) interactions. This results in skyrmion-like spin textures and large topological Hall effects near room temperature in NiFeMo films. Theoretical simulations of DM interactions closely match experimental results, confirming the presence of skyrmion-like spin textures in the films. Manipulating topology and magnetism in NiFeMo thin films through strain engineering could provide valuable insights for developing spintronic devices based on the quantum Hall effect.