Anomalous Hall Effect In Topological Magnetic Materials

In recent years, topological semimetals have emerged as a new frontier in the condensed matter community. With the interplay between the structural asymmetry and spin-orbit interaction, and details of Berry phase, new topological states are being discovered. Though inversion symmetry breaking Weyl fermion is demonstrated in TaAs family of compounds, the time-reversal breaking examples remain elusive. Here we demonstrate the formation of magnetic nodal lines in a topological magnetic Heusler compound Co₂MnGa. Without spin-orbit coupling (SOC), we find three nodal lines due to the band crossing in majority spin channel. With SOC, nodal lines split up giving rise to the Weyl nodes, whose momentum space distributions depend on the magnetization direction. We observe giant anomalous Hall conductivity of ~ 1600 Ω^-1cm^-1 with room temperature anomalous Hall angle ~12% in Co₂MnGa. In-fact, by suitable manipulations of the crystal symmetries and the band structures of the materials, one can selectively tuned the anomalous Hall conductivity from 0 to values up to 1600 Ω^-1cm^-1 in various magnetic Heusler compounds for next-generation topo-spintronics applications.