Effects of magnetism on the electronic structure and pairing mechanism in oxide superconductors

Generalized tight-binding method is developed to strongly correlated electron systems. Evolution of the band structure of CuO _2 layer with hole doping from the undoped charge transfer antiferromagnetic insulator to the optimally doped paramagnetic metal is obtained. Effective low energy Hamiltonian is given by a t-J-I model that allows to compare magnetic mechanism and symmetry of pairing in cuprates and ruthenates on equal footing.