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Construction of artificial media possessing a negative index of refraction can be simplified by using a nonconducting ferrimagnetic host medium to provide a negative permeability and an array of conducting wires to provide a negative permittivity. The interaction between the ferrimagnet and the wire array, which destroys the negative permittivity of the wire array, can be overcome by cladding the wires with an insulating, nonmagnetic jacket. Calculations of the propagation constants and transmission coefficients for a square array of cladded wires in a ferrimagnetic host are presented. The calculations are near exact for wavelengths significantly greater than the lattice parameter of the wire array. For wires a few microns in diameter, a lattice constant of 0.8mm, and an appropriate ferrimagnetic host in a biasing magnetic field, a transmission band 0.5GHz wide centered near 16GHz exhibits a negative index of refraction. Losses in the ferrimagnet and impedance mismatch to vacuum limit the peak transmission amplitude ratio through a slab 3.0cm thick to ≈3%.

No abstract

Recent interest has been generated in composite materials for which both the dielectric constant and the magnetic permeability are negative. These composites behave as if they possess a negative index of refraction, although the broader, less specific adjective "left-handed" has also been applied to them. Such composites possess two sets of structures which are separately responsible for the negative ∊ and μ. However, materials having a negative μ are common in the microwave frequency range and such a material can replace one set of structures in the composite. An example of a simple composite is a YIG medium (μ<0) penetrated by sets of metallic strips or wires which give rise a negative dielectric constant in the appropriate frequency range. The index of refraction of the composite can be modulated by adjusting the applied magnetic field.

Ferromagnetic antiresonance (FMAR) transmission measurements at 24 GHz, and at temperatures between 20°C and 364"C, are reportedforpolycrystalline nickel foil 20pm thick. The results can be described by the usual equation of motion for the magnetization and using a Landau-Lifshitz damping parameter of 2.45 -c 0. l x 108 s-' and a g factor of 2.187 -c 0.005, both temperature independent. The temperature independence of the damping was confirmed by measurements of the maximum transmission amplitude at FMAR as a function of temperature. The data were corrected for magnetostrictive effects in order LO obtain the g factor and magnetization.