The effect of O vacancies upon the electronic and magnetic properties of La0.66Sr0.33MnO3 was investigated by means of ab initio calculations within the density-functional formalism, combined with photo-emission. The simulations showed that the introduction of O vacancies caused a shift of the valence-band features towards higher binding energies and an increase in the degree of covalency of Mn bonding. The Mn magnetic moments underwent some changes, while keeping the situation relatively close to that of the ideal non-defective system. In none of the various vacancy configurations, did a drastic charge or spin rearrangement occur. However, there was an important vacancy-induced drawback. The half-metallicity which was typical of the perfectly stoichiometric system was usually lost, due to defective bands that crossed the Fermi level. Photo-emission experiments performed on epitaxial thin films with various contents of O vacancies, grown by pulsed-laser deposition, tended to confirm the theoretical predictions. The results clearly indicated that control of the O-deficiency should be experimentally achieved in order to avoid unwanted consequences in terms of spin-injection efficiency.

Oxygen Vacancies and Induced Changes in the Electronic and Magnetic Structures of La0.66Sr0.33MnO3 - a Combined ab initio and Photoemission Study. S.Picozzi, C.Ma, Z.Yang, R.Bertacco, M.Cantoni, A.Cattoni, D.Petti, S.Brivio, F.Ciccacci: Physical Review B, 2007, 75[9], 094418 (11pp)