Emergence of asymmetric skew-scattering dominated anomalous Nernst effect in spin gapless semiconductors Co_1+xFe_1-xCrGa

Heusler alloy-based spin gapless semiconductors (SGSs) with very high Curie temperatures (T_C) have recently gained enormous attention because of their unconventional electronic structures. They exhibit a zero band gap in one of the spin channels and a non-zero band gap in the other spin channel, making them a promising class of materials for tunable spin transport. Here, we report the first ever experimental observation of anomalous Nernst effect (ANE) in Co_1+xFe_1−xCrGa (x = 0, 0.2, 0.4, and 0.5), which are the emerging quaternary Heusler alloy-based SGSs (Phys. Rev. B 99, 104429 (2019)). Our findings reveal that the electron-electron elastic scattering and the disorder mediated weak localization effect play the major roles in electrical transport for all the samples at low temperatures, whereas the magnon-drag effect dominates the longitudinal thermoelectric transport. The ANE coefficient at room temperature increases from ≈ 0.018 μV. K^-1 for <!--[if gte msEquation 12]> style='mso-bidi-font-style:normal'>x=0 to ≈ 0.063 μV. K^-1 for <!--[if gte msEquation 12]> style='mso-bidi-font-style:normal'>x=0.5 , which is higher than that for Ni₈₁Fe₁₉ and compressively strained SrRuO₃ films. Furthermore, the ANE coefficient decreases gradually with lowering temperature for all the samples. Our analysis indicates that the observed ANE in these samples originates from asymmetric skew-scattering of charge carriers.