Spin chirality induced large topological Hall effect in magnetic Weyl semimetallic Eu₂Ir₂O₇ (111) epitaxial thin film

Rare earth pyrochlore iridates RE₂Ir₂O₇ are predicted to be magnetic Weyl semimetallic (WSM) materials in the presence of electron correlation (U) and spin-orbit coupling (l) . Here we have studied the magnetotransport properties of epitaxial Eu₂Ir₂O₇ (111) thin film grown on YSZ by solid phase epitaxy technique. Low-temperature longitudinal resistivity (ρ_xx) data shows a power-law dependence on temperature, which signifies semimetallic charge transport. By varying the film thickness, the semimetallic charge transport is tuned to realize the predicted WSM phase. The Hall resistivity (ρ_xy) data exhibits an anomalous Hall effect (AHE), in the temperature range of 2–25 K. The intrinsic AHE is explained in terms momentum space Berry curvature of the Weyl nodes. In addition to the AHE an large topological Hall effect (THE) is observed in the temperature range of 2–5 K. Due to scalar spin chirality generated by the all-in-all-out (AIAO) non-coplanar spin structure of Ir⁴⁺ moments, the conduction electrons acquire a real-space Berry curvature and causes a large THE. Low-temperature (2–10 K) magnetoresistance (MR) data shows a non-hysteretic large negative MR, causes by reduction in scattering by the spin canting. For temperature of 15 K and above, MR shows hysteretic behavior up to the 90 K (metal-semimetal transition temperature). The hysteretic MR suggest magnetic field-induced domain imbalance of Ir⁴⁺ moments.