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

Abstract

In this paper, arguments are provided to support that, in passive media, the imaginary part of the permeability can take positive and negative values. These arguments are based on the analysis of two different situations: i) the hydrodynamical model and ii) the spatially dispersive effective parameters of a multilayered structure. In addition, the electromagnetic energy is considered in a medium described by a spatially dispersive permittivity tensor.