- Ferromagnetic materials show spontaneous magnetization without an external field below the
critical temperature. - The emerging order can only be explained quantum mechanically (Pauli principle, exchange
interaction). - A mathematical basis is the Heisenberg hamiltonian. It can be solved in mean field theory. This
is done in treating the exchange energy as an additional magnetic field resulting from the nearest
neighbors. - Using a statistical approach for the occupation of the spin levels and the magnetic field ob-
tained from the mean field calcualtion one can find a relation between the magnetization and
temperature.
axel boer
(Axel Boer)
#1