First principle study of the magnetism of Sr<Subscript>2</Subscript>CoMoO<Subscript>6-δ</Subscript> (δ=0, 1/2) double perovskites

We investigate the electronic structure of bulk Sr<Subscript>2</Subscript>CoMoO<Subscript>6-δ</Subscript> double perovskites using the ab initio Full Potential Linearized Augmented Plane Wave method in order to study their magnetic properties within the GGA and GGA+U methods. We discuss the relative stability of ferromagnetic (FM) and antiferromagnetic (AFM) orders (i) without and with taking into account the observed tilting of the oxygen octahedra and (ii) by introducing oxygen vacancies. We show that a very good agreement with experimental results — AFM order for δ= 0 and FM order for δ= 1/2 — is obtained only when the tilting of the oxygen tetrahedra is taking into account and when the GGA+U method is used. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2006