MOLECULAR EM FIELDS AND DYNAMICAL RESPONSES IN SOLIDS WITH MAGNETIC CHARGES

The monopoles are theoretically deflned as charges which produce flelds whose divergence is, obviously, difierent from zero. However, the entities which have been experimentally detected in the spin-ices, with mimetic behavior to that of the magnetic monopoles, generate magnetic flelds which seem to be compatible with r¢B = 0. This apparent contradiction can create confusion and therefore it requires explanation. In this paper we have carried out an analysis of the difierent electromagnetic flelds in the spin- ices materials. We clarify the difierences between the average flelds of standard Maxwell equations with zero divergence even in spin-ices and the non macroscopic flelds when there are magnetic monopoles in these materials. We give the molecular or local flelds which allow us to determine the molecular polarizability. We combine the extended Clausius-Mossotti equations with the Lorentz-Drude model for obtaining the extended susceptibility and the optical conductivity which can be used for explaining the action of the electromagnetic flelds in spin-ices.