Large anomalous Nernst effect in polycrystalline topological half-metal Co2CrGa

Recent breakthroughs in the study of topological magnets have blazed a new trail for the development of thermoelectrics harnessing the anomalous Nernst effect (ANE). In recent years, a multitude of theoretical and experimental investigations have confirmed that Co 2 -based Heusler alloys, e.g. Co 2 MnGa (Sakai et al., Ref. 1), present a giant anomalous Hall effect (AHE), which arises out of their non-trivial electronic band structure . In this work, a comprehensive investigation on the magnetic, thermal, electrical, and thermoelectric properties is carried out for Co 2 CrGa Heusler polycrystalline alloy, with a particular emphasis on the ANE. Our research reveals Co 2 CrGa alloy possesses a high Curie temperature of ∼530 K and a large saturation magnetization of ∼2.36 μ B /f. u. at 300 K. It is found that electron-electron elastic scattering dominates the longitudinal electrical transport in the low-temperature regime of this system, whereas electron-phonon scattering prevails in the high-temperature. Likewise, the magnon-phonon scattering plays a leading role in the longitudinal thermoelectric transport at the low-temperature range with a sign change in S xx at 250 K due to the competition between spin-up and spin-down sub-bands. The anomalous Nernst coefficient | S y x A | reaches a large value of ∼1 μV K −1 at 300 K, and correspondingly anomalous transverse thermoelectric conductivity (ANC, α y x A ) reaches up to ∼0.6 A m −1 K −1 . With careful analysis, it follows that both the ANE and AHE in this alloy are attributed to the intrinsic Berry curvature contribution. Additionally, it is demonstrated that the contribution of transverse voltage ( S y x I ), which is directly driven by the ANC α y x A , significantly exceeds the one of AHE that acts on the thermally generated carrier flow induced by the longitudinal Seebeck effect( S y x I I ). This work represents a novel Heusler alloy as a transverse thermoelectric material , offering a theoretical foundation and versatile platform for further exploration of ANE control in this material system, such as chemical doping strategy. • Study of the magnetic, electrical and thermoelectric properties of Co 2 CrGa highlights the anomalous Nernst effect (ANE). • Dominant magnon-phonon scattering and a sign change exist in longitudinal thermoelectric transport. • Both the anomalous Hall effect (AHE) and the large ANE are driven by intrinsic Berry curvature contributions in Co 2 CrGa. • Chemical doping strategy could potentially enhance the topological transport properties.