Structural Stability, Opto-Electronic, Magnetic and Thermoelectric Properties of Half-Metallic Ferromagnets Quaternary Heusler Alloys CoFeXAs (X = Mn, Cr and V)

The Quaternary Heusler alloys CoFeXAs (X = Cr, Mn and V) fully spin-polarized with half-metallic stability, show low direct band gap, high absorption in the ultraviolet light, high spin polarization and adequate Seebeck coefficient. CoFeCrAs, CoFeMnAs and CoFeVAs have an integer magnetic moment of 4 μB, 5 μB and 3 μB according to the Slater-Pauling rule. The obtained minimal energy favors the type I CoFeVAs alloy over the type III CoFeCrAs and CoFeMnAs alloys. For CoFeCrAs and CoFeMnAs alloys, there is no band gap close to the Fermi level in the minority-spin, suggesting that they are direct Г–Г band gap semiconductors. Three-dimensional Co, Fe, and Mn atoms hybridized strongly, with little input from V and As atoms. Co, Fe, Cr, and Mn all have parallel magnetic moments, which results in ferromagnetic interactions between these atoms and gives these elements their ferromagnetic character.