Interfacial Topological Hall Effect

• Interfacial Topological Hall Effect is a phenomenon driven by real-space Berry curvature from chiral spin textures at material interfaces.
• It relies on interfacial Dzyaloshinskii–Moriya interaction, strong spin–orbit coupling, and inversion symmetry breaking to stabilize Néel-type skyrmions and other chiral structures.
• The effect enables electrical detection and manipulation of topological spin states in both metallic and insulating systems, paving the way for advanced spintronic memory and logic applications.

The Interfacial Topological Hall Effect (ITHE) describes a class of Hall transport phenomena originating from real-space Berry curvature induced by chiral spin textures localized at, or imprinted through, material interfaces. Unlike the conventional topological Hall effect (THE), which is typically observed in homogeneous conducting magnets hosting skyrmions, ITHE encompasses both metallic and insulating systems, including those where topological spin structures are stabilized or transferred by engineering interfacial exchange, spin–orbit coupling, and inversion symmetry breaking. ITHE serves as a sensitive probe of noncoplanar magnetism and is fundamental for the electrical detection and manipulation of topological spin states in complex heterostructures, underpinning a range of spintronic, memory, and logic applications.

1. Interfacial Dzyaloshinskii–Moriya Interaction and Inversion Symmetry Breaking

At the core of ITHE is the Dzyaloshinskii–Moriya interaction (DMI), which arises at interfaces where inversion symmetry is broken and one or both constituents exhibit strong spin–orbit coupling. For example, in SrRuO₃/SrIrO₃ bilayers, DMI emerges strictly at the interface due to pronounced SOC from the 5d electrons of SrIrO₃ and the lack of inversion symmetry. The interface DMI is described, for a 2D lattice, by

$$E_{\rm DM} = D \sum_{i} \left[ \hat{y} \cdot (\mathbf{n}_i \times \mathbf{n}_{i+x}) - \hat{x} \cdot (\mathbf{n}_i \times \mathbf{n}_{i+y}) \right],$$

where $D$ is the coupling constant and $\mathbf{n}_i$ is the unit vector of the local moment at site $i$. This term energetically favors twisting (chirality) in the spin configuration, leading to the stabilization of Néel-type skyrmions at the interface (Matsuno et al., 2016).

The physical origin and magnitude of interfacial DMI are contingent on both constituents: heavy metals (Pt, SrIrO₃, Bi₂Te₃) introduce strong SOC, while thin magnetic layers (SrRuO₃, NiCo₂O₄, MnGa) provide the exchange and anisotropy energies necessary for the interplay. The effective DMI acting on a ferromagnetic layer of thickness $m$ is diluted as $D_{\rm eff} = D/m$, suppressing ITHE beyond a critical thickness (Matsuno et al., 2016).

2. Stabilization of Chiral Spin Textures and Topological Hall Transport

Interfacial DMI, competing with ferromagnetic exchange ($J$) and magnetic anisotropy ($K$), stabilizes noncoplanar spin textures such as Néel-type skyrmions, bubble domains, and spin spirals. When conduction electrons (or spin carriers generated via the spin Hall effect) traverse these spin textures, they acquire a real-space Berry phase, which manifests as an emergent magnetic field $\mathbf{B}_{\rm eff}$. For isolated skyrmions of density $n_{\rm sk}$,

$\mathbf{B}_{\rm eff} = n_{\rm sk} \phi_0,$

($\phi_0 = h/e$) yields an extra transverse Hall resistivity component:

$\rho_H^{(T)} = P R_0 n_{\rm sk} \phi_0,$

where $P$ denotes spin polarization and $R_0$ the ordinary Hall coefficient (Matsuno et al., 2016). ITHE signals can thus be interpreted via the skyrmion density and their topological charge. Experimentally, skyrmion sizes as small as 10–20 nm have been inferred, indicating high interfacial DMI and dense chiral spin textures (Matsuno et al., 2016, Giri et al., 18 Feb 2025, Zhang et al., 2021).

Mechanism extends to other systems: interfacial exchange bias in ferrimagnetic/antiferromagnetic manganese nitride films mediates DMI at phase boundaries, resulting in noncollinear spin texture and robust ITHE (Meng et al., 2017). In Pt/NiCo₂O₄, heavy-metal proximity and perpendicular magnetic anisotropy promote small, dense magnetic nucleation centers topologically equivalent to skyrmions, giving a giant ITHE—even at 2–350 K (Giri et al., 18 Feb 2025). In van der Waals heterostructures (CrTe₂/Bi₂Te₃), the atomically sharp interface and strong SOC drive optimal DMI, enhancing ITHE magnitudes (~1.39 μΩ·cm) (Zhang et al., 2021).

3. Quantum Corrections and Scaling of ITHE

Quantum interference further modifies ITHE. Gradient corrections to the kinetic equation (arising from inhomogeneous magnetization) introduce weak localization contributions to the Hall conductivity in 2D systems (Liu et al., 2022). The quantum correction to the topological Hall conductivity $\delta\sigma_{yx}^{g}$ is logarithmic in the phase coherence length $l_\phi$ and the mean free path $l$:

$$\delta\sigma_{yx}^{g} = \frac{e^2}{\hbar} \frac{1}{4\pi^2} \frac{\hbar}{\epsilon_F\tau} \frac{\hbar}{M\tau} \frac{e\tau B_t}{m} \ln \left( \frac{l_\phi}{l} \right),$$

where $B_t$ encodes the winding number (skyrmion density) and magnetization gradients—parameters tunable by interfacial engineering (Liu et al., 2022). These corrections are experimentally observable in dilute magnetic semiconductors.

ITHE magnitude also exhibits power-law scaling near phase transitions (isolated skyrmions vs. skyrmion lattice), with fluctuation-enhanced THE persisting over broad temperature-field ranges; critical exponents $\beta$ and $\gamma$ govern the scaling (Raju et al., 2021).

4. Artificial and Non-Topological ITHE-like Features

The interpretation of ITHE must contend with artefactual Hall signals arising from inhomogeneous magnetic profiles or superposition of anomalous Hall contributions. For instance, spatially varying interdomain coupling ($\alpha$) across structured interfaces, modeled via modified Jiles–Atherton hysteresis, introduces nonuniform magnetization $\Delta M$, yielding additional Hall resistivity:

$\rho_H = \rho_0 H + R_a M' + R_a \Delta M,$

where $\Delta M$ mimics THE even in the absence of true topological spin textures (Bhattacharya et al., 2021). Similarly, sandwich heterostructures stacking magnetic TI layers of opposite Berry curvature engineer artificial topological Hall effect–like features via superposition rather than chiral spin states (Wang et al., 2020). These results necessitate careful experimental distinction between genuine ITHE (Berry-phase driven by noncoplanar textures) and composite or extrinsic signatures (Gerber, 2018, Bhattacharya et al., 2021).

5. ITHE in Insulating Magnets: Magnetic Proximity Effect and Spin Hall Topological Hall Effect

Electrical detection of topological spin textures in insulating magnets is enabled via proximity-induced ITHE (Li et al., 16 Sep 2025) or spin-Hall topological Hall effect (SH-THE) (Ahmed et al., 2019). In Pt/h-LuFeO₃, the insulating h-LuFeO₃ hosts a robust 120° triangular spin lattice with canting, resulting in topological spin structure but negligible net magnetization. The magnetic proximity effect imprints this texture onto adjacent Pt nanoclusters, which then display an ITHE that persists up to 14 T and yields a Hall-conductivity/magnetization ratio (>2 V⁻¹) far exceeding classic AHE factors (Li et al., 16 Sep 2025). SH-THE in Pt/Tm₃Fe₅O₁₂ operates by spin-current injection from Pt (via SHE), with interfacial spin–orbit torque sampling skyrmion configurations in the insulator and transducing a Berry-phase Hall signal (Ahmed et al., 2019).

Notably, these mechanisms extend topological Hall transport to insulating magnets and allow electrical readout of spin topology irrespective of large magnetization, with persistent ITHE signals distinguishing themselves from narrow THE peaks characteristic of metallic systems (Ahmed et al., 2019, Li et al., 16 Sep 2025).

6. Tunability, Chirality Control, and Spintronic Implications

Interfacial engineering offers precise control over ITHE magnitude, chirality, and phase diagram. By tuning layer thickness (e.g., SrRuO₃ < 7 unit cells for strong effect), interfacial DMI, and magnetic anisotropy, chiral magnetic states are tuned in density, size, and topological charge (Matsuno et al., 2016, Meng et al., 2017). The resultant ITHE can be manipulated by electric field, strain, or substrate choices, enabling room-temperature operation of skyrmion-based memory and logic. The field and temperature tunability in oxides (Pt/NiCo₂O₄, CaMnO₃/CaIrO₃/CaMnO₃) further allows for design of devices with robust operation windows (Giri et al., 18 Feb 2025, Lim et al., 2020). Skyrmion dynamics, including low threshold current motion observed in oxide trilayers (Lim et al., 2020), are foundational for racetrack memory and energy-efficient spintronic devices.

Emergent applications encompass high-density, low-power memory, logic, sensors, and fundamental studies of quantum magnetism and topological charge. ITHE uniquely enables electrical detection and manipulation of topological spin textures in insulating films, hybrid van der Waals systems, and oxide heterostructures, expanding the landscape for future spintronic technologies (Giri et al., 18 Feb 2025, Li et al., 16 Sep 2025, Zhang et al., 2021).

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Summary Table of Key ITHE Mechanisms and Model Systems

System	Stabilizing Mechanism	ITHE Feature
SrRuO₃/SrIrO₃	Interfacial DMI, broken inversion	Tunable Néel skyrmions, thickness-dependent suppression
Pt/NiCo₂O₄	Interfacial DMI, PMA	Giant THE, high skyrmion density, 2–350 K range
CrTe₂/Bi₂Te₃	Atomically sharp interface, SOC	Giant THE, optimized DMI, quantum surface states
Pt/h-LuFeO₃	Magnetic proximity effect	Persistent ITHE, electrical readout in insulators
CaMnO₃/CaIrO₃/CaMnO₃	Charge transfer, stacking faults	ITHE, STT-driven skyrmion motion, interface asymmetry
MnGa/Heavy Metal Bilayer	Interfacial DMI, exchange/aniso.	Robust THE over 5–300 K, tunable via D_c
MnBi (size-tuned)	Intrinsic chirality, mesoscopic bubbles	Sample-size-dependent coexistence of THE mechanisms

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Conclusion

Interfacial Topological Hall Effect is a fundamentally versatile phenomenon that emerges from real-space Berry curvature associated with chiral spin configurations at engineered interfaces. It is controlled by the interplay of interfacial DMI, symmetry breaking, spin–orbit physics, and heterostructure geometry. ITHE not only provides a platform for robust detection and manipulation of topological spin states in thin films and hybrid heterostructures but is also a preeminent mechanism for extending topological charge transport to insulating magnets and broadening the functional reach of spintronic technologies.