Ab initio predictions of stability, half-metallicity and magnetism in Co₂NbAl and Co₂ZrAl full-Heusler alloys

This paper reports ab initio computed results of stability, phonon, electronic, magnetic, and surface properties of Co₂NbAl and Co₂ZrAl full-Heusler alloys. These alloys are stable, which is confirmed by formation energy, cohesive energy, and phonon spectra. The total magnetic moments of these alloys follow the Slater-Pauling (SP) rule (M_t = Z_t-24). The Nb (111) and Al (111)-terminations of Co₂NbAl show half-metallic characteristic, while other terminations are metallic due to the majority density of states (DOS) and the minority DOS at the Fermi level. CoCrNbAl and CoCrZrAl show half-metallicity while CoMnZrAl and CoFeNbAl exhibit metallic nature after the substitution of Cr, Mn, and Fe atom in Co₂NbAl and Co₂ZrAl, respectively. The electronic structures exhibit the band gaps of 0.39 eV, 0.24 eV, and 1.19 eV for CoFeNbAl, CoCrNbAl, and CoCrZrAl, respectively. The calculated values of the magnetic moments are in good agreement with experimental data. The results confirm that Co₂NbAl, Co₂ZrAl, CoFeNbAl, CoCrNbAl, and CoCrZrAl can be promising alloys for spintronic devices.