Itinerant electron systems

The reduced orbital overlap between the radicals reduces the bandwidth and the electronic structures could be better considered as those of a localised rather than itinerant electron system. This poor overlap results in very small antiferromagnetic interactions being observed, and the compounds behave as nearly perfect Curie-Weiss paramagnets. In the cases when improved lateral interactions between the stacks are achieved by change of the substituents85 the compounds behave as weak ID ferromagnets due to the effective orthogonality of the S C interactions. 

The above picture is in a good agreement with the theory of itinerant electron systems with interplay between superconductivity and magnetism [8], In that theory, an itinerant SDW gap may appear at the Fermi surface only before an SC gap, i.e. in the normal state. This SDW gap is highly anisotropic since it is only formed at symmetric parts of the Fermi surface [8] ( see, fig.2). Its width ASDW being unusually large for an SC gap, well conforms to that for an SDW gap because of inequality ASc < ASDW... 

More importantly, it is easy to keep track of every parameter in a very careful way. When I say parameter, it might be parameters which have real life correspondences, like the volume of the sample, or parameters from a model you have made up yourself, like the local moment in a Heisenberg model of an itinerant electron system. This is an enormous advantage, and especially the possibility to measure made up variables makes it possible to try to understand the physics in terms of models that perhaps can be generalized to even more materials than the one examined, thus giving predictive power to the scientist. 

For concentrated Kondo systems orbitally driven anisotropic hybridization of the f electrons with conduction electrons is crucial (Cooper et al. 1988, Levy and Zhang 1989). The anisotropic part of the mixing interaction causes a substructure within the rather narrow f band, which leads to crystal-field effects even in highly itinerant-electron systems. On account of this crystal-field dressing a localized 5f electron in NpSnj might develop. 

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