SEMINAR 2024

Heusler alloy-based spin gapless semiconductors (SGS) with very high Curie temperatures (TC) exhibit zero bandgap in one of the spin channels and a non-zero bandgap in the other spin channel, making them a promising class of materials for tunable spin transport. Our group has recently reported the first experimental observation of Anomalous Nernst Effect (ANE) in polycrystalline quaternary Heusler CoFeCrGa [1] as well as thin films grown on MgO substrates [2]. The results reveal that the ANE originates from asymmetric skew-scattering of charge carriers and the thin films show ANE coefficients nearly two orders of magnitude higher and comparable to that of Weyl semimetal Co2MnGa thin films. In quaternary Heusler Weyl semimetals CoFeVSb, our experiments combining magneto-thermal transport, RF transverse susceptibility and FMR have revealed fascinating topological aspects and the dominance of intrinsic Berry phase due to the presence of Weyl points predicted by DFT calculations [3]. Finally, we present for the first time a possible efficient thermopile device that utilizes the combination of positive and negative ANE in quaternary Heusler alloys (CrRuXGe, X=Co and Mn) [4]. Overall, this talk would present key aspects of thermally driven spin currents in Heusler alloys and their integration into spin caloritronic heterostructures.

1. “Emergence of asymmetric skew-scattering dominated anomalous Nernst effect in spin gapless semiconductors Co1+xFe1-xCrGa” – Amit Chanda, Deepika Rani, Jadupati Nag, Aftab Alam, KG Suresh, Manh-Huong Phan, Hari Srikanth, Phys. Rev. B 106, 134416 (2022)
2. “Large thermo-spin effects in Heusler alloy-based spin gapless semiconductor thin films” -A. Chanda, Deepika Rani, D. DeTellem, N. Alzahrani, D. A. Arena, S. Witanachchi, Ratnamala Chatterjee, M.H. Phan and Hari Srikanth, ACS Applied Materials & Interfaces 15, 53697 (2023)
3. “Intrinsic Berry curvature driven anomalous Nernst thermopower in the semimetallic Heusler alloy CoFeVSb” -A. Chanda, J. Nag, A. Alam, K.G. Suresh, M.H. Phan and H. Srikanth, Physical Review B (LETTER) 107, L220403 (2023)
4. “Large anomalous Nernst effect and its bipolarity in quaternary equiatomic Heusler alloys CrRuXGe (X = Co and Mn)” -A. Chanda, J. Nag, N. Schulz, A. Alam, K.G. Suresh, M.H. Phan and H. Srikanth, Physical Review B109, 224415 (2024)