J. Hubbard
Phys. Rev. B 19, 2626 – Published 1 March 1979
ABSTRACT
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.
DOI:https://doi.org/10.1103/PhysRevB.19.2626
©1979 American Physical Society
Magnetism of iron. II
J. Hubbard
Phys. Rev. B 20, 4584 – Published 1 December 1979
ABSTRACT
A previously developed theory of the magnetism of iron, based upon the notion of a randomized exchange field, is modified and extended. It is shown that Coulomb fields arise in association with the randomized exchange field; the modification allows one to take into account these fields, which are found to change the details of the previous results without affecting the main conclusions. The theory has been extended to calculate the properties of the model at finite temperatures: the Curie temperature (1840 K), the magnetization curve, the paramagnetic susceptibility (a Curie-Weiss law), and the effective interatomic exchange coupling are calculated for iron. The magnitudes of the atomic spin moments were found to vary little up to 1.5 times the Curie temperature.
DOI:https://doi.org/10.1103/PhysRevB.20.4584
©1979 American Physical Society
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