Magnetism Pauli type behavior

Hund s rule, like the Pauli exclusion principle, is based on experiment It is possible to determine the number of unpaired electrons in an atom. With solids, this is done by studying their behavior in a magnetic field. If there are unpaired electrons present the solid will be attracted into the field. Such a substance is said to be paramagnetic. If the atoms in the solid contain only paired electrons, it is slightly repelled by the field. Substances of this type are called diamagnetic. With gaseous atoms, the atomic spectrum can also be used to establish the presence and number of unpaired electrons. 

Many explanations have been given to account for the departures from the expected enhanced-Pauli Xs in the metallic regime [3]. First, we have to consider if the compound that we are studying has one or two magnetic stacks. If it has two, we should try to separate the contributions from each one. This has been done successfully in a number of cases. The decomposition can be done through the g factor or through the Knight shift. Second, if a chain is metallic, the susceptibility should, in principle, be Pauli-like. If there are localized spins, the behavior should be of Bonner-Fisher type. 

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