Research Projects

The observation of anomalous transport phenomena—such as the topological Hall effect (THE) —at thin film interfaces of ferromagnetic complex oxides holds significant promise for both fundamental research and technological applications. THE typically arises from non-coplanar spin textures that form due to inversion symmetry breaking and spin-orbit coupling at magnetic interfaces. However, a key challenge remains: identifying materials that exhibit large THEs near room temperature and under low magnetic fields suitable for device integration. In our recent work, we demonstrated sizable room-temperature THEs in epitaxial permalloy (Py) thin films, attributed to interfacial strain-induced inversion symmetry breaking and noncoplanar spin configurations (ACS Appl. Mater. Interfaces 17, 8692 (2025)). Further studies showed that coupling Py with the half-metallic ferromagnet La₀.₆₅Sr₀.₃₅MnO₃ (LSMO) in Py/LSMO heterostructures [arXiv:2501.09969 (2025)] leads to even larger THEs. These effects are further amplified by introducing ferroelectric BaTiO₃ layers, forming Py/BTO/LSMO sandwich structures. The enhancement is attributed to the interplay between robust ferromagnetism and Rashba-type spin-orbit coupling at the engineered interfaces. Building on these findings, our proposal has three primary goals: (1) Engineer interfacial strain in epitaxial magnetic metal and alloy thin films to realize strong THEs at room temperature and low magnetic fields. (2) Leverage interfacial Rashba interactions to induce giant THEs in heterostructures combining ferromagnetic oxides and spin-orbit coupled magnetic alloys. (3) Control THE via electric field gating in metal/oxide heterostructures with integrated ferroelectric layers, enabling voltage-tunable Hall resistivity through modulation of the Rashba interaction. We also seek to develop a comprehensive theoretical framework to elucidate the physical mechanisms underlying these transport effects. Using first-principles calculations, we will explore how strain and external electric fields impact electronic structure—particularly Rashba interactions and Berry curvature, key contributors to anomalous Hall conductivity. The proposed research underscores the complex interplay between exchange interactions, spin-orbit coupling, lattice distortions, symmetry breaking, and charge transfer at engineered interfaces, with promising implications for future spintronic technologies.