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 co-efficient. CoFeCrAs, CoFeMnAs and CoFeVAs have an integer magnetic moment of 4 mu B, 5 mu B and 3 mu B 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 T -T 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.