First-principles calculation of oxygen vacancy effects on the magnetic properties of the perovskite SrNiO3

Nickelates have been studied extensively due to their intriguing physical properties, but less attention has been paid to the properties of divalent A-site cation perovskite nickelates with a formal valence state of 4+ for Ni. Here, we study the electronic and magnetic properties of perovskite ${\mathrm{SrNiO}}_{3\ensuremath{-}\ensuremath{\delta}}$ with an oxygen deficiency \ensuremath{\delta} up to 0.375 using density functional theory. Because of the strong covalency and negative charge transfer energetics, the structure is predicted to exhibit ligand holes , with Ni present as ${d}^{8}{\underline{L}}^{2}$ or ${d}^{7}\underline{L}$ and significant magnetic moment at the oxygen sites. The ground state for $\ensuremath{\delta}=0--0.375$ consists of ferromagnetically ordered Ni with the Ni and O moments coupled antiferromagnetically, and the removal of oxygen increases the net magnetization. These behaviors are also predicted for other A-site cations such as Ca and Ba. This work demonstrates the importance of ligand holes in oxides with formally high valence Ni, including their influence on the magnetic properties, and motivates further experimental study of the electronic and magnetic properties of nickelates with divalent A-site cations.