Anomalous planar Hall effect in predicted type II Weyl Fe3Sn2

Abstract

We have investigated various electronic transport properties such as the anisotropic magnetoresistance, planar Hall effect, and anomalous Hall effect in kagome Fe3Sn2, which has been predicted to be a type II Weyl metal. Based on magnetortransport, we determine the spin reorientation transition to peak at 120 K and coexistence of both out of plane and in plane phases at temperatures around the spin reorientation, indicative of a first order phase transition. In planar Hall effect, we discover a field antisymmetric contribution in addition to the standard field symmetric contribution. This field antisymmetric planar Hall effect has an in-plane 3-fold rotational symmetry, which is distinctively different from the symmetric counterpart. Furthermore, the temperature and field dependence of the field antisymmetric contribution is different from both the symmetric planar Hall effect and anomalous Hall effect, pointing to a different origin. A linear and antisymmetric planar Hall effect is predicted to be present in the case of non-magnetic Weyl semimetals. The experimental signatures in our case fit well with the prediction in addition to reflecting contributions from its ferromagnetism. As the magnetization of Fe3Sn2 has a 3-fold rotational degeneracy, the associated band structure and Weyl nodes determined by the magnetization direction owing to the spin-orbit coupling will have accordingly a 3-fold rotational degeneracy giving rise to the 3-fold antisymmetric PHE. We thus propose that the antisymmetric PHE that we discovered is the realization of an antisymmetric and linear planar Hall effect due to the presence of Weyl nodes near the Fermi level in a time reversal symmetry broken system. Our finding offers a promising route for macroscopically probing Weyl systems.