On effective electromagnetic parameters of artificial nanostructured magnetic materials

In this paper we discuss effective material parameter description of new nanostructures designed to perform as artificial magnetic materials for visible light. Among these structures there are various split-ring resonators, dual-bar structures, fishnet layers and other geometries. Artificial magnetic response in these structures appears due to weak spatial dispersion effects, and it is important to study the conditions under which the magnetic response can be adequately measured with effective permeability tensor. On the examples of dual bars and split rings we show that this is possible only under some quite restrictive conditions. In the general case, more complicated constitutive relations with more effective material parameters need to be developed.