With the use of a model Hamiltonian and retarded double time green's function formalism, we obtain mathematical expressions for spin density wave and superconductivity parameters. The model reveals a distinct possibility of the coexistence of magnetic phase and superconductivity, which are two usually irreconcilable cooperative phenomena. The work is motivated by the recent experimental evidences of coexistence of spin density wave and superconductivity in a number of FeAs-based superconductors. The theoretical results are then applied to show the coexistence of spin density wave and superconductivity in iron pnictide compound Ba1−xKxFe2As2 (0.2 ≤ x < 0.4).

-Starting with a model Hamiltonian for the system with equal spin singlet and triplet pairings based on quantum field theory and green function formalism, we obtain expressions for superconductivity and ferromagnetism parameters. The model exhibits a distinct possibility of the coexistence of superconductivity and ferromagnetism, which are two usually irreconcilable cooperative phenomena, however, recently ferromagnetism and superconductivity have been shown to coexist simultaneously in the newly discovered compounds such as UCoGe, UIr and UGe 2 .The work is motivated by the recent experimental evidences below the superconducting phase temperature in a number of uranium-based superconductors. The theoretical results are then applied to show the coexistence of superconductivity and ferromagnetism in the intermetallic uraniumbased compound UCoGe, UIr and UGe 2 . The limitations of the model are also discussed.

A model is presented utilizing a Hamiltonian with equal spin singlet and triplet pairings based on quantum field theory and green function formalism, to show the correlation between the superconducting and spin density wave (SDW) order parameters. The model exhibits a distinct possibility of the coexistence of superconductivity and long-range magnetic phase, which are two usually incompatible cooperative phenomena. The work is motivated by the recent experimental evidences on high-T C superconductivity in the FeAs-based superconductors. The theoretical results are then applied to show the coexistence of superconductivity and spin density wave (SDW) in NaFe 1-x Co x As.