DFT-based exploration of XMnCrZ (X = Ni, Ti; Z = Sn, Sb) quaternary heusler alloys for structural and multifunctional properties

Equiatomic quaternary Heusler alloys have recently emerged as promising multifunctional materials due to their tunable structural order, robust magnetism, and versatile transport properties. In this work, we present a comprehensive first-principles investigation of equiatomic X MnCr Z ( \(X = Ti, Ni;\ Z = Sb, Sn\) ) alloys using density functional theory (DFT) and density functional perturbation theory (DFPT). Electronic structure analysis shows that \(TiMnCrSb\) and \(TiMnCrSn\) exhibit half-metallicity with nearly 100% spin polarization, in excellent agreement with the Slater–Pauling rule, while Ni-based alloys retain metallic behavior. The magnetic moments are primarily carried by Mn and Cr atoms, with Ti- and Ni-based alloys displaying distinct magnetic exchange interactions. The thermoelectric properties evaluated at the Fermi level reveal positive Seebeck coefficients for the Ni-based alloys and negative values for the Ti-based compounds. However, upon tuning the Fermi level to an optimal energy, \(TiMnCrSb\) exhibits a remarkable enhancement in its Seebeck coefficient, reaching a maximum of \(450.7~μ V/K\) at room temperature. While the other materials also display noticeable increases, \(TiMnCrSb\) stands out as the most promising candidate for efficient thermoelectric and multifunctional applications among the investigated EQHAs.