A Material definition attaches one or several tensor field definitions to a physical domain. Materials are defined in the file materials.jcm. It is only allowed to set material properties within a Material section (no impressed quantities). For instance, one may fix the relative permittivity and the relative permeability for a certain domain:

# sets a constant relative permeability and permittivity
Material {
  DomainId = 2
  RelPermittivity = ...
  RelPermeability = ...

To capture complex physical situations the definition of the material property tensor fields can be defined accordingly. For example, the relative permittivity may be affected by the presence of mechanical stresses due photo-elastic effects. Examples are given in subsequent sections.