Electronic structure of metallic ferromagnets above the Curie temperature

The authors describe the electronic structure of Fe and Ni above their Curie temperatures in their disordered local moment (DLM) states as a function of wavevector k and energy epsilon . In particular, they calculate the Bloch spectral function, A(k, epsilon ), averaged over the orientational configurations of the local moments, at selected points in the Brillouin zone and determine the shape and smearing of the 'Fermi surface'. They find that BCC Fe, with a local moment of 1.9 mu _B, can show an exchange splitting at some points whilst in other regions of the Brillouin zone no such splitting occurs. For comparison they also study FCC Fe, which also supports a substantial local moment. They find that it has similar features but the smearing of the 'bands' is more pronounced. On the other hand, the electronic structure of Ni is quite different, shows no such local exchange splitting, but is able to support a small local moment of 0.2 mu _B. The resulting picture of the electronic structure of Ni is that of a paramagnetic smeared 'Stoner-Wohlfarth' model.