Ceria is a transparent and high dielectric constant rare-earth oxide, whose fluorite structure matches well with silicon. It promises good integrability for spintronic devices, even for non stoichiometric compounds. Co doped CeO₂ has attracted particular interest due to its ferromagnetic behaviour observed well above room temperature for low doping concentration. However there is controversy among different experimental results regarding critical temperatures and values of the magnetic moments as a function of doping concentration.

The presence of oxygen vacancies has been considered as a possible factor affecting the FM response in the case of films, but it is not clear whether it induces Co clustering and/or promotes magnetic ordering.

In this work we explore the role played by oxygen vacancies on the magnetic properties of bulk Ceria as a function of Co doping concentration, considering a homogeneous distribution of the impurities and, follow the evolution of the magnetic interactions with the number of oxygen vacancies per Co. This study is done by performing LSDA+U calculations and by taking into account the presence of Ce³⁺ in reduced Ceria along the lattice relaxation process.