We propose and prove that it is possible to decouple the electric and magnetic response of an array of conductive nanoparticles and realize a very wide range of combinations of effective permittivities and permeabilities. The principle exploits the large differences in the Thomas-Fermi screening length for longitudinal electric fields and the classical penetration depth for time-varying transverse magnetic fields. This non-resonant principle allows frequency invariance of the effective material properties with a bandwidth spanning many octaves, orders of magnitude larger than previous resonant metamaterials. An effective medium with a record-high refractive index over broad-band is demonstrated as an example. Published by AIP Publishing