First-principles prediction of the quaternary half-metallic ferromagnets TiZrIrZ (Z= Al, Ga or In) for spintronics applications

Inspired by the unique properties and potential applications especially in spintronics, here we investigate the structure and electronic properties of the bulk TiZrIrZ (Z = Al, Ga or In) quaternary Heusler alloys and their (001)-oriented thin films by using first-principles calculations. The results show that all the bulk TiZrIrZ alloys are half-metallic ferromagnets with a total magnetic moment mu(t) of 2 mu(B)/f. u., satisfying the Slater-Pauling rule mu(t)= Z(t) - 18. Their spin-down band gaps are resulted from the d-d hybridizations between the transition metal elements Ti, Zr and Ir. The large absolute values of both positive cohesive energies and negative formation energies indicate these three alloys are thermodynamically stable and can be fabricated experimentally. The nonappearances of negative phonon frequency demonstrate their dynamic stability. Furthermore, their (001)-oriented thin films with natural ZrZ (Z= Al, Ga or In) terminations are still half-metallic ferromagnets and thus useable in spintronics and magnetoelectronics fields.