The magnetism of iron

A type of theory capable of reconciling the localized- and itinerant-electron models of a ferromagnetic metal is discussed. This kind of theory contemplates a distribution of "exchange field" configurations which correspond very roughly to the spin configurations of the localized model. Computations involve thermal averages over these configurations, each configuration V having an effective energy E(V). Starting from the band structure for ferromagnetic iron, the E(V) have been estimated for certain configurations V. The results are reasonably consistent with the observed Curie temperature of iron, in spite of the presence of exchange fields ∼1-2 eV, and give some suggestion of behavior characteristic of the Heisenberg model. © 1979 The American Physical Society.