Enhanced ferromagnetism in half-metallic CoIrZrAl quaternary Heusler alloy: A density functional study

The possibility of synthesis of the quaternary Heusler alloy CoIrZrAl is proposed on the basis of first-principles Density Functional calculations. The equilibrium lattice constant, assuming F-43 m lattice symmetry, is calculated and the Bulk modulus obtained is very close to that of Co2ZrAl (Essaoud and Jbara, 2021). CoIrZrAl Heusler alloy is predicted to be a half-metal having an energy gap of 0.7632 eV between t1u and eu state in the spin down channel. The ferromagnetic state is the magnetic ground state where the main source of total magnetic moment (= 1 mu B) is the unpaired electron in the eu state derived from Co-3d and Ir-5d electrons. Upon 50% doping at the Co-site (3d) by an Ir atom having extended 5d state increases the mean field estimate of TCover Co2ZrAl. The charge density difference profile clearly establishes that the exchange mechanism is super-exchange between hybrid Co-3d electrons and Ir-5d electrons mediated by their hybridization with Zr4d electrons. The partial replacement of the Co-3d electrons with less localized Ir-5d electrons leads to robust ferromagnetism and robust half-metallicity under hydrostatic pressure.