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Register a new userGiant enhancement of anomalous Hall effect in Cr modulation-doped non-collinear antiferromagnetic Mn3Sn thin films
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We report on Cr doping effect in Mn3Sn polycrystalline films with both uniform and modulation doping. It is found that Cr doping with low concentration does not cause notable changes to the structural and magnetic properties of Mn3Sn, but it significantly enhances the anomalous Hall conductivity, particularly for modulation-doped samples at low temperature. A Hall conductivity as high as 184.8 {Omega}-1 cm-1 is obtained for modulation-doped samples at 50 K, in a sharp contrast to vanishingly small values for undoped samples at the same temperature. We attribute the enhancement to the change of Fermi level induced by Cr doping
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Magnetotransport is at the center of the spintronics. Mn3Sn, an antiferromagnet that has a noncollinear 120{deg} spin order, exhibits large anomalous Hall effect (AHE) at room temperature. But such a behavior has been remained elusive in Mn3Sn films. Here we report the observation of robust AHE up to room temperature in quasi-epitaxial Mn3Sn thin films, prepared by magnetron sputtering. The growth of both (11-20)- and (0001)-oriented Mn3Sn films provides a unique opportunity for comparing AHE in three different measurement configurations. When the magnetic field is swept along (0001) plane, such as the direction of [01-10] and [2-1-10] the films show comparatively higher anomalous Hall conductivity than its perpendicular counterpart ([0001]), irrespective of their respectively orthogonal current along [0001] or [01-10]. A quite weak ferromagnetic moment of 3 emu/cm^3 is obtained in (11-20)-oriented Mn3Sn films, guaranteeing the switching of the Hall signals with magnetization reversal. Our finding would advance the integration of Mn3Sn in antiferromagnetic spintronics.
We show that the spin-orbit coupling (SOC) in alpha-MnTe impacts the transport behavior by generating an anisotropic valence-band splitting, resulting in four spin-polarized pockets near Gamma. A minimal k-dot-p model is constructed to capture this splitting by group theory analysis, a tight-binding model and ab initio calculations. The model is shown to describe the rotation symmetry of the zero-field planer Hall effect (PHE). The upper limit of the PHE percentage is shown to be fundamentally determined by the band shape, and is quantitatively estimated to be roughly 31% by first principles.
We have studied the anomalous Hall effect (AHE) in strained thin films of the frustrated antiferromagnet Mn$_{3}$NiN. The AHE does not follow the conventional relationships with magnetization or longitudinal conductivity and is enhanced relative to that expected from the magnetization in the antiferromagnetic state below $T_{mathrm{N}} = 260$,K. This enhancement is consistent with origins from the non-collinear antiferromagnetic structure, as the latter is closely related to that found in Mn$_{3}$Ir and Mn$_{3}$Pt where a large AHE is induced by the Berry curvature. As the Berry phase induced AHE should scale with spin-orbit coupling, yet larger AHE may be found in other members of the chemically flexible Mn$_{3}A$N structure.
Strong electronic correlations can produce remarkable phenomena such as metal-insulator transitions and greatly enhance superconductivity, thermoelectricity, or optical non-linearity. In correlated systems, spatially varying charge textures also amplify magnetoelectric effects or electroresistance in mesostructures. However, how spatially varying spin textures may influence electron transport in the presence of correlations remains unclear. Here we demonstrate a very large topological Hall effect (THE) in thin films of a lightly electron-doped charge-transfer insulator, (Ca, Ce)MnO3. Magnetic force microscopy reveals the presence of magnetic bubbles, whose density vs. magnetic field peaks near the THE maximum, as is expected to occur in skyrmion systems. The THE critically depends on carrier concentration and diverges at low doping, near the metal-insulator transition. We discuss the strong amplification of the THE by correlation effects and give perspectives for its non-volatile control by electric fields.
The two dimensional kagome spin lattice structure of Mn atoms in the family of Mn$_3$X non-collinear antiferromagnets are providing substantial excitement in the exploration of Berry curvature physics and the associated non-trivial magnetotransport responses. Much of these studies are performed in the hexagonal systems, mainly Mn$_3$Sn and Mn$_3$Ge, with the kagome planes having their normal along the [001] direction. In this manuscript, we report our study in the cubic Mn$_3$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 $Omega^{-1}$cm$^{-1}$ at room temperature to 29 $Omega^{-1}$cm$^{-1}$ 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 temperature, below 70 K, caused by the reorientation of Mn moments out of the kagome plane. Our above results in thin films of Mn$_3$Pt make advances in their integration with room temperature antiferromagnetic spintronics.
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