Derivation of effective parameters of magnetic metamaterials composed of   passive resonant LC inclusions
  We determine rigorously the effective permeability of magnetic metamaterials composed of passive particles exhibiting magnetic resonances. The effective permeability is expressed in terms of circuit parameters characteristic to these particles (L, C, and R) and particle geometry. The derivation takes into account the magnetic coupling between particles. We show that a bigger concentration of particles leads to an improvement in the metamaterial performances (such as bandwidth or loss tangent), but this effect saturates as the particles are packed more tightly. The theory is validated through numerical simulations of physically realizable metamaterials. 
Bogdan-Ioan Popa and Steven A. Cummer