Unusual magnetic and electronic properties of Al-substituted Ga₂MnNi: An ab initio study

Searching for new Heusler alloys with novel electronic and magnetic properties is a recent topic of interest to researchers. Using density functional theory based calculations, we study the effect of the replacement of Ga by Al at the A-site of A₂BC-type alloy, Ga₂MnNi. By analyzing the magnetic properties of the Ga_2-xAl_xMnNi system (with values of x between 0 and 2), we find that in Al₂MnNi alloy, the Mn atom possesses a substantially lower value of moment compared to Ga₂MnNi. To understand this unusual result, atom-derived spin-polarized densities of states (DOS) for the Ga_2-xAl_xMnNi system have been calculated. Analysis of Bader charge and difference charge density distribution has been found to corroborate with the DOS results. Further, we find that Al₂MnNi alloy has a relatively large DOS, rather close to and below the Fermi level. Hence, electronic properties of a system with partial substitution of Ni by Co at the C-site of Al₂MnNi have been probed. Combined results of calculations of Bloch spectral functions and density of states of this material suggest a large DOS almost at the Fermi level.