Observation of Non-linear hall effect in Polycrystalline magnetic multilayes

The Nonlinear Hall effect(NLHE) driven principally by the Berry curvature dipole has been established in non-centrosymmetric vander Waals crystals, topological semimetals, and moir\'e superlattices, but its extension to technologically mature heavy-metal/ferromagnet multilayer platforms remains largely unexplored. Here, we report the observation of a robust NLHE in polycrystalline magnetic multilayers, persisting from 2 K to room temperature. The second-harmonic transverse voltage is independent of both excitation frequency and applied out-of-plane magnetic field, while the vanishingly small third-harmonic response confirms that the observed signal is not dominated by a quantum-metric contribution and instead reflects a genuine second-order electronic response. A scaling analysis of the second-order Hall conductivity against the longitudinal conductivity identifies a dominant, conductivity-independent term establishing the intrinsic berry curvature dipole. Our theoretical analysis, supported by first-principles DFT calculations, further satisfies and corroborates the experimental results. These results establish sputter-deposited polycrystalline thin film as the first engineered magnetic multilayer platform for BCD-driven nonlinear Hall transport, extending the NLHE material landscape beyond van der Waals systems into scalable, industry-compatible thin-film spintronic architectures suitable for high frequency rectifications and nonlinear sensors.