Magnetic Aspects of Superconducting Pairing

We discuss some of the recently proposed models dealing with the superconducting state in the presence of strong antiferromagnetic fluctuations, induced by the on-site Coulomb repulsion between electrons (the Hubbard correlation). In the weak coupling limit we treat the influence of correlation effects on the phonon-mediated superconductivity within the BCS-Eliashberg framework. As a non-standard model in this limit we describe next the so-called spin bag model. To discuss strong correlation limit, we describe first the projected Hamiltonian (the t-J Hamiltonian) and the corresponding antiferromagnetic state. The resonating valence bond model is introduced both as a naive version, equivalent to the BCS treatment of the transverse spin fluctuations, as well as a holon-spinon version