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 (V_O) and the Oxygen interstitial (O_i) 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 BaSrNiWO_6−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 (V_O) and the Oxygen interstitial (O_i) in the BaSrNiWO₆ compound. We showed that the formation of V_O is easier and vice versa for the O_i formation. The obtained results reveal(V_O) and the Oxygen interstitial (O_i) that the anti-ferromagnetic can be converted to ferromagnetic in the double perovskite BaSrNiWO₆ induced by Oxygen vacancies V_O. - Highlights: • We have studied the ferromagnetism and Half Metallicity in Double Perovskite BaSrNiWO₆. • We have applied the Ab-inito calculations using the DFT approach. • We showed the effects induced by Oxygen Vacancies and Oxygen interstitial. • We found that the magnetic ordering in BaSrNiWO_6−δ depends on the position of the Oxygen vacancy in the unit cell.