Magnetism from conductors and enhanced nonlinear phenomena

We show that microstructures built from nonmagnetic conducting sheets exhib it an effective magnetic permeability mu(eff), which can be tuned to values not accessible in naturally occurring materials, including large imaginary components of mu(eff). The microstructure is on a scale much less than the wavelength of radiation, is not resolved by incident microwaves, and uses a very low density of metal so that structures can be extremely lightweight . Most of the structures are resonant due to internal capacitance and induc tance, and resonant enhancement combined with compression of electrical ene rgy into a very small volume greatly enhances the energy density at critica l locations in the structure, easily by factors of a million and possibly b y much more, Weakly nonlinear materials placed at these critical locations will show greatly enhanced effects raising the possibility of manufacturing active structures whose properties can be switched at will between many st ates.