Planar Hall effect and Anisotropic Magnetoresistance in Thin Films of Chiral Antiferromagnet Mn3Sn (2307.07795v1)

Abstract: Antiferromagnetic Weyl semimetals with spin chirality offer excellent platforms to address the Berry phase physics, which manifests prominently in several of their electro-optical and electro-magnetic responses including as a large anomalous Hall effect (AHE) and spin Hall conductivity. Here, we report measurements of magneto-transport in c-axis textured Mn3Sn thin films grown on the [111] plane of single crystal MgO. At room temperature, these films display a weak uncompensated magnetic moment of \approx 0.12 \micro_{B}/f.u. in the basal plane and a longitudinal resistivity (\rho_{xx}) close to \approx 3.8 \micro\Omega.m. A residual resistivity ration (\rho_{xx} (300 K)/\rho_{xx} (2 K)) of \approx 3.92 further indicates the high quality of the films. While at 300 K a weak AHE together with field-linear Hall resistivity (\rho_{xy}) is observed in magnetic fields (H) applied perpendicular to the Kagome planes, the temperature (T) dependence of \rho_{xy} shows prominent signatures of three magnetic phases in the temperature regime of 2 to 300 K. The \rho_{xy} also derives a non-trivial topological contribution (\r{ho}THE \approx 1n\Omega.m) in the spin glass phase which appears at T \geq 100 K. Our measurements of anisotropic magnetoresistance (AMR) and planar Hall effect (PHE) over a wide H-T phase space reveal the hitherto unseen effects in the three magnetic phases of Mn3Sn. While the AMR and PHE are negative in the inverse triangular spin phase (250 K \geq T \geq TN), the helical phase (100 \geq T \geq 250 K) is devoid of anisotropic in-plane resistivity, and the spin glass phase shows a sign reversal of AMR with the increasing magnetic field. The origin of this sign change in AMR/PHE is attributed to the emergence of topologically protected spin textures like skyrmions where the fictitious effective magnetic field is estimated to be \approx 4.4 tesla.