  A detailed review is given on the evolution of the theory of itinerant
magnetism. The self-consistent renormalization (SCR) theory is quite successful
in addressing the phenomenon of itinerant magnetism in weakly and nearly
ferromagnetic and anti-ferromagnetic materials. It goes beyond the Stoner and
random phase approximation (RPA) theories in taking the correlation effects
into account. The Mathematical machinery of the SCR theory is rather
complicated. The aim of these notes is to provide the required background. The
problems with Stoner and RPA theory are discussed and the way in which the SCR
theory rectifies those problems is also discussed.
