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

Abstract

The first-principle density functional theory (DFT) calculations were employed to investigate the electronic structures, magnetic properties and half-metallicity of $\text {Ti}_{2}\text {IrZ}$ (Z $=$ B, Al, Ga, and In) Heusler alloys with $\text {AlCu}_{2}\text {Mn}$- and $\text {CuHg}_{2}\text {Ti}$-type structures within local density approximation and generalised gradient approximation for the exchange correlation potential. It was found that $\text {CuHg}_{2}\text {Ti}$-type structure in ferromagnetic state was energetically more favourable than $\text {AlCu}_{2}\text {Mn}$-type structure in all compounds except $\text {Ti}_{2}\text {IrB}$ which was stable in $\text {AlCu}_{2}\text {Mn}$-type structure in non-magnetic state. $\text {Ti}_{2}\text {IrZ}$ (Z $=$ B, Al, Ga, and In) alloys in $\text {CuHg}_{2}\text {Ti}$-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 $\text {Ti}_{2}\text {IrB}$, $\text {Ti}_{2}\text {IrAl}$, $\text {Ti}_{2}\text {IrGa}$, and $\text {Ti}_{2}\text {IrIn}$. The origin of half-metallicity was discussed for $\text {Ti}_{2}\text {IrGa}$ using the energy band structure. The total magnetic moments of $\text {Ti}_{2}\text {IrZ}$ (Z $=$ B, Al, Ga, and In) compounds in $\text {CuHg}_{2}\text {Ti}$-type structure were obtained as $2\mu _{\mathrm{B}}$ per formula unit, which were in agreement with Slater–Pauling rule ($M_{\mathrm{tot}} =Z_{\mathrm{tot}}-$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.