Sign reversal of anomalous Hall conductivity and magnetoresistance in cubic noncollinear antiferromagnet Mn3Pt thin films

The two-dimensional kagome spin lattice structure of Mn atoms in the family of ${\mathrm{Mn}}_{3}X$ noncollinear antiferromagnets are providing substantial excitement in the exploration of Berry-curvature physics and the associated nontrivial magnetotransport responses. Much of these studies are performed in the hexagonal systems, mainly ${\mathrm{Mn}}_{3}\mathrm{Sn}$ and ${\mathrm{Mn}}_{3}\mathrm{Ge}$ with the kagome planes having their normal along the [001] direction. In this paper, we report our study in the cubic ${\mathrm{Mn}}_{3}\mathrm{Pt}$ thin films with their kagome planes normal to the [111] crystal axis. Our studies reveal a hole conduction dominant Hall response with a non-monotonic temperature dependence of anomalous Hall conductivity (AHC), increasing from $9\phantom{\rule{0.28em}{0ex}}{\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ at room temperature to $29\phantom{\rule{0.28em}{0ex}}{\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ at 100 K, followed by a drop and unexpected sign reversal at lower temperatures. Similar sign reversal is also observed in magnetoresistance measurements. We attribute this sign reversal to the transition from a Berry-curvature-dominated AHC at high temperature to a weak canted ferromagnetic AHC response at lower temperatures below 70 K caused by the reorientation of Mn moments out of the kagome plane. Our above results in thin films of ${\mathrm{Mn}}_{3}\mathrm{Pt}$ make advances in their integration with room-temperature antiferromagnetic spintronics.