Oxygen vacancies and induced changes in the electronic and magnetic structures of La0.66Sr0.33MnO3:: A combined ab initio and photoemission study

The effect of oxygen vacancies on the electronic and magnetic properties of La0.66Sr0.33MnO3 (LSMO) has been investigated by means of ab initio calculations within the density-functional formalism combined with photoemission. The simulations show that the introduction of oxygen vacancies causes a shift of the valence-band features toward higher binding energies and an increase of the degree of covalency of Mn bondings. The Mn magnetic moments undergo some changes, keeping, however, the situation relatively close to the ideal nondefective system: in none of the different vacancy configurations, a drastic charge or spin rearrangement occurs. There is, though, an important vacancy-induced drawback: half-metallicity, typical of the perfectly stoichiometric system, is generally lost due to defective bands that cross the Fermi level. Photoemission experiments performed on epitaxial thin films of LSMO with different contents of oxygen vacancies grown by pulsed laser deposition essentially confirm theoretical predictions. Our findings clearly indicate that the control over oxygen deficiency should therefore be experimentally achieved to avoid unwanted consequences in terms of spin-injection efficiency.