Multifunctional Behavior of New full Heusler Mn2CoZ (Z = Tl,Bi) Alloys

In this study, we comprehensively investigate the structural, electronic, mag- netic, thermoelectric, and optical characteristics of novel Heusler alloys Mn2CoTl and Mn2CoBi, employing density functional theory (DFT) in conjunction with semi-classical Boltzmann transport theory. Through analysis of the band structure and density of states (DOS), we unequivocally demonstrate the ferromagnetic half- metallic nature of the two Heusler alloys highlighting their potential for applications in spintronic devices. Moreover, our calculations reveal spin magnetic moments con- sistent with Slater-Pauling behavior. Additionally, the investigated Heusler alloys exhibit superior dielectric characteristics. Examination of the maximum reflectivity and absorption spectra demonstrates that the Mn2CoBi structure displays enhanced optical response in the visible domain compared to Mn2CoTl which favors the UV region. Regarding transport properties, the full Heusler alloys exhibit remarkably low lattice conductivity, leading to exceptional thermoelectric performance with record ZT values reaching up to 0.85 at 300K using GGA, and 0.93 at 500K based en HSE method for Mn2CoTl and Mn2CoBi, respectively. This assesses the considerable promise of full Heusler alloys as both low- and high-temperature thermoelectric ma- terials.