Exploration of highly correlated Co‐based quaternary Heusler alloys for spintronics and thermoelectric applications

The half-metallic character of new quaternary Heusler alloys CoXMnAs (X = Ru, Rh) is established along with their thermoelectric, mechanical, and thermodynamic properties. The optimization of energy suggests that alloys are stable in Y2-type structure with a ferromagnetic character. The electronic band profile through generalized gradient approximation and modified Becke-Johnson potential indicates the metallic character of alloys. However, with inclusion of Hubbard potential to generalized gradient approximation, the alloys depict half-metallic character with semiconducting nature in spin-down state. The alloys possess high magnetic moment, CoRuMnAs has 5 μB, whereas CoRhMnAs has 6 μB, following Slater-Pauling rule MT = ZT − 24. The narrow band gap in spin-down channel enhances the thermoelectric properties. The maximum value for thermopower (|S|) obtained is 44.3 and 53.44 μV/K for CoRuMnAs and CoRhMnAs, respectively. The variation of electrical conductivity, Seebeck coefficient, and figure of merit affirm increasing trend with temperature, which is a good indication of materials to be used in thermoelectric technology. The mechanical stability along with ductile nature of alloys is determined through elastic constants. Further, we have calculated thermodynamic properties and have established their dependence on temperature and pressure using quasi-harmonic Debye model. The half-metallic nature with efficient thermoelectric parameters strongly supports the possible application of alloys for spin devices and green energy generation.

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