Left-handed materials in metallic magnetic granular composites

There is recently interests in the "left-handed" materials. In these materials the direction of the wave vector of electromagnetic radiation is opposite to the direction of the energy flow. We present simple arguments that suggests that magnetic composites can also be left-handed materials. However, the physics involved seems to be different from the original argument. In our argument, the imaginary part of the dielectric constant is much larger than the real part, opposite to the original argument. (C) 2003 Elsevier B.V. All rights reserved.