ABSTRACT
Among the various forms of electronic order in condensed matter, magnetism takes a special place. Ferrromagnetism has been known for several thousand years, but new forms of magnetism are being discovered at an increasing rate. The theoretical understanding of magnetism, similarly, has a long history and continues to present interesting challenges. Moreover, it appears increasingly plausible that further to the magnetic structure itself, deviations away from the ordered structure, magnetic fluctuations, can couple to the electrons from which the magnetic order arises in the first place, and lead to novel electronic states, such as unconventional superconductivity. This section aims to give a brief introduction to elements of the theory of magnetism in solids.
