Ferromagnetism and half metallicity induced by oxygen vacancies in the double perovskite BaSrNiWO6: DFT study

Using the spin polarized density functional theory (DFT) and exploring the Plane-Wave Self-Consistent Field (PWscf) code implemented in Quantum-ESPRESSO package, we investigate the effect of the Oxygen vacancies (VO) and the Oxygen interstitial (Oi) on the double perovskite BaSrNiWO6. This deals with the magnetic ordering and the electronic structure in such a pure sample exhibiting the insulating anti-ferromagnetic (AFM) state. This study shows that the presence of oxygen deficient defects converts the insulating to half metal with ferromagnetic or anti-ferromagnetic states. The magnetic ordering in BaSrNiWO6−δ depends on the position of the Oxygen vacancy in the unit cell. However, it has been shown that the Oxygen interstitial preserves the anti-ferromagnetic propriety. We have computed the formation energies of different positions of the Oxygen vacancy (VO) and the Oxygen interstitial (Oi) in the BaSrNiWO6 compound. We showed that the formation of VO is easier and vice versa for the Oi formation. The obtained results reveal(VO) and the Oxygen interstitial (Oi) that the anti-ferromagnetic can be converted to ferromagnetic in the double perovskite BaSrNiWO6 induced by Oxygen vacancies VO.