Investigation of the electronic, magnetic, and thermoelectric characteristics of the transition metal-based double perovskites Ba2XNbO6 (X = V, Cr, Mn, and Fe) for spintronic applications.

Spin-polarized materials with high Curie temperatures are emerging aspirants for spintronics. In the present work, we conduct first-principles calculations using the WIEN2k code to examine the structural, electronic, magnetic, and thermoelectric properties of Ba2XNbO6 (X = V, Cr, Mn, and Fe). The thermodynamic stability is confirmed by the negative enthalpies of formation and the structural stability by the tolerance factor. The range of Curie temperatures (T c) from 289 K to 325 K for the studied materials allows for room-temperature ferromagnetism. Inferring from their spin-polarized band structures, Ba2VNbO6 and Ba2MnNbO6 have half-metallic ferromagnetism, and Ba2CrNbO6 and Ba2FeNbO6 have ferromagnetic semiconductor behavior. The calculated exchange and crystal field energies and exchange constants reveal dominant spin-orbit coupling rather than magnetic ion clustering. The total magnetic moment analysis demonstrates that the magnetic moment ranges from 2.0µ B to 5.00µ B for the Fe-based compounds, reflecting the gradual addition of electrons to the 3d orbitals, and its distribution to non-magnetic sites confirms the exchange of electrons. Additionally, these compounds show great potential in thermoelectrics. Ba2VNbO6 reached a power factor of 8.60 W mK-2 because of its good electrical conductivity and moderate Seebeck coefficient. These results underscore that substituting the B-site elements in Ba2XNbO6 (X = V, Cr, Mn, and Fe) can improve the spintronic and thermoelectric properties by modifying the electronic structure, magnetic behavior, and measurable thermoelectric power.