Anomalous Hall Effect in Epitaxial Thin Films of the Hexagonal Heusler MnPtGa Noncollinear Hard Magnet

Magnetic systems exhibiting spin-canted states have garnered much attention recently for their promising rich exotic properties driven by the real-space spin textures and competing magnetic orders. We report here on the magnetic groundtstate and Berry curvature-driven intrinsic anomalous Hall effect (AHE) of hexagonal Heusler MnPtGa epitaxial thin films.

The centrosymmetric MnPtGa films grown by magnetron sputtering on (0001)-Al₂O₃ crystallize with an out-of-plane c-axis crystal orientation, along which they exhibit preferential perpendicular magnetic anisotropy below their Curie temperature (T_C = 263 K). Below a thermally induced spin reorientation transition at 160 K, the magnetic groundtstate, determined by single-crystal neutron diffraction, is found to be a noncollinear spin canted state where the Mn moments tilt 20° away from the c-axis [1].

Furthermore, the anomalous Hall conductivity (AHC) of MnPtGa epitaxial films is found to exhibit a strongly nonmonotonic behaviour as a function of temperature, whereby the AHC changes sign at T^* = 110 K; for all investigated films’ thicknesses (20-60 nm). This hints at a common – intrinsic – mechanism governing both the sign of the AHC and the magnitude of the AHE. Our findings, supported by first-principle calculations, strongly suggest an anomalous Hall effect of intrinsic origin, driven by a momentum-space Berry curvature mechanism [2].

[1] R. Ibarra, E. Lesne et al., Appl. Phys. Lett. 120, 172403 (2022). [2] Adv. Mater. Interfaces (accepted).