Sign reversal of anomalous Hall effect in polycrystalline ultrathin Mn₃Pt films

The kagome structure of noncolinear antiferromagnet (NC-AFM) gives rise to finite Berry curvature which consequences many novel phenomena such as anomalous Hall effect (AHE), magneto optical Kerr effect and topological Hall effect¹. Although AHE has been reported in epitaxial thin films of NC-AFM, Mn₃Pt², here we present the sign reversal of AHE in polycrystalline Mn₃Pt films varying the thickness of the film and measurement temperature.
Polycrystalline Mn₃Pt films of thickness 5-25 nm have been grown on SiO₂ substrate using co-sputtering technique. X-ray diffraction reveals the phase purity of our samples. Electrical transport has been carried out in Hall bar geometry prepared by optical lithography and Ar ion etching. We observe negative Hall resistivity (ρ_AH) at 300 K which changes sign ~ 10 K. In addition to that, we also observe nearly linear positive magnetoresistance (MR) at high temperature regime (300 to 15 K). Similar to the ρ_AH, MR becomes negative at the same temperature. We attribute this sign reversal due to the rotation of Mn moments confirmed from the temperature dependent of magnetization data³.
1. Chen et al., Phys. Rev. Lett., 112, 017205, 2014.
2. Liu et. al., Nature Electronics, 1, 172, 2018.
3. Muduli et. al., Phys. Rev. B 99, 184425, 2019.