Half-metallic ferromagnetism in $m{Ti_{2}IrZ (Z = B, Al, Ga, and In)}$ Heusler alloys: A density functional study

摘要

The first-principle density functional theory (DFT) calculations were employed to investigate the electronic structures, magnetic properties and half-metallicity of $m{Ti_{2}IrZ (Z = B, Al, Ga, and In)}$ Heusler alloys with $m{AlCu_{2}Mn-}$ and $m{CuHg_{2}Ti-}$type structures within local density approximation and generalised gradient approximation for the exchange correlation potential. It was found that $m{CuHg_{2}Ti-}$type structure in ferromagnetic state was energetically more favourable than $m{AlCu_{2}Mn-}$type structure in all compounds except $m{Ti_{2}IrB}$ which was stable in $m{AlCu_{2}Mn-}$type structure in non-magnetic state. $m{Ti_{2}IrZ (Z = B, Al, Ga, and In)}$ alloys in $m{CuHg_{2}Ti-}$type structure were half-metallic ferromagnets at their equilibrium lattice constants. Half-metallic band gaps were respectively equal to 0.87, 0.79, 0.75, and 0.73 eV for $m{Ti_{2}IrB}$, $m{Ti_{2}IrAl}$, $m{Ti_{2}IrGa}$, and $m{Ti_{2}IrIn}$. The origin of half-metallicity was discussed for $m{Ti_{2}IrGa}$ using the energy band structure. The total magnetic moments of $m{Ti_{2}IrZ (Z = B, Al, Ga, and In)}$ compounds in $m{CuHg_{2}Ti}$-type structure were obtained as $2mu_{B}$ per formula unit, which were in agreement with Slatera??Pauling rule $(M_{tot} = Z_{tot}a??18)$. All the four compounds were half-metals in a wide range of lattice constants indicating that they may be suitable and promising materials for future spintronic applications.