arXiv:1001.2531v1[cond-mat.mtrl-sci]14 Jan 2010 Ab initio study of magnetism at the TiO$_{2}$/LaAlO$_{3}$ interface Mariana Weissmann ∗ and V. Ferrari † Departamento de F´ısica, Comisi ´on Nacional de Energ´ıa Atomica, Avda. del Libertador 8250, 1429 Buenos Aires, Argentina Centre Interdisciplinaire de Nanoscience de Marseille, CNRS, Campus de Luminy, Case 913, 13288 Marseille Cedex 9, France ‡ (Dated: November 1, 2018) In this paper we study the possible relation between the electronic and magnetic structure of the TiO$_{2}$/LaAlO$_{3}$ interface and the unexpected magnetism found in undoped TiO$_{2}$ films grown on LaAlO $_{3}$. We concentrate on the role played by structural relaxation and interfacial oxygen vacancies. LaAlO$_{3}$ has a layered structure along the (001) direction with alternating LaO and AlO$_{2}$ planes, with nominal charges of +1 and -1, respectively. As a consequence of that, an oxygen deficient TiO 2 film with anatase structure will grow preferently on the AlO$_{2}$ surface layer. We have therefore performed ab-initio calculations for superlattices with TiO$_{2}$/AlO$_{2}$ interfaces with interfacial oxygen vacancies. Our main results are that vacancies lead to a change in the valence state of neighbour Ti atoms but not necessarily to a magnetic solution and that the appearance of magnetism depends also on structural details, such as second neighbor positions. These results are obtained using both the LSDA and LSDA+U approximations. Keywords: oxides, magnetism, ab-initio calculation Abstract 1 Andr´ es Sa´ ul