Half-metallic ferromagnetism in $$\text {Ti}_{2}\text {IrZ}$$ Ti 2 I r Z (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.

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