Spatial dispersion and the sign of the imaginary part of the permeability

Abstract

The modelling of the magnetic permeability is addressed in the frame of spatially dispersive media. Different situations are analyzed: i) the hydrodynamical model; ii) the spatially dispersive effective parameters of a multilayered structure; iii) the electromagnetic energy in a medium described by a spatially dispersive permittivity tensor. All these situations support that, in passive media, the imaginary part of the permeability can take positive and negative values.