Negative permeability of magnetic nanocomposite films for designing left-handed metamaterials

We have theoretically evaluated magnetic permeability of Ni nanocomposite films, in which the dipolar interactions between the Ni particles are considered explicitly. A numerical model of the nanocomposite is constructed according to our recent experimental results and a micromagnetic calculation is conducted. We show that the value of permeability strongly depends on the volume fraction and randomness of the particles. Particularly, as the randomness of the particles increases, the negative value of permeability drastically shrinks. However, the region of applied field, where the permeability is negative, becomes broader. This is advantageous for the broadband left-handed metamaterials in microwave regions.