Phase transitions in quasi-two-dimensional systems doped with atoms with different valences, at various temperatures are investigated. The transitions into the magnetic state of spin density wave which appear due to the nesting on the Fermi surface and the transition into incommensurable state of spin density wave are considered along with the appearnce of superconductivity. The main system of equation is presented, the difference of free energies in different phases, superconducting transition temperature and heat capacity jump are calculated. The behavior of mentioned quantities as a function of temperature and charge carrier density is researched.