Gyromagnetic Material Research Articles

Waveguide Type Optical Modulator Using Kerr Magnetooptic Effects in Ni–Fe Thin Films: Theoretical Study

A fundamental analysis of modes in a dielectric guide fabricated on a lossy gyromagnetic substrate has been developed for a thin film waveguide type optical modulator application experimentally discussed in the preceding paper. It is shown that when the substrate is of gyromagnetic material, the propagating modes become hybrid in character. Phase and attenuation curves as well as wave function profiles for such type of modes are computed. Power flow characteristics for the HE0 mode are also discussed. A comparison with the experimental results reported earlier has been made.

Effects of a gyromagnetic material in a double-coupled helix traveling-wave tube

An analysis of the double-coupled helix with a gyromagnetic material (ferrite) inside the inner helix is presented using the field theory approach. Quantitative results are presented for the slow-wave solution. Qualitative results in the form of graphs illustrate wave propagation characteristics, impedance, resonance effects, and electric field variations for typical values of the ferrite parameters. The nonreciprocal nature of the ferrite material is demonstrated. Also, some important aspects of ferrite are pointed out which give support to the view that this type of material may improve traveling-wave tube operation.

Loss properties of cylindrical waveguides containing gyromagnetic media

The system considered is a waveguide of radius a containing a concentric rod of gyromagnetic material of radius b. The attenuation constant is given by where ɛ, μ, and α are the relative permittivity and the relative permeability elements of the rod, and ɛ″, μ″, α″ are their imaginary parts. The quantities ∂β/∂ɛ, ∂β/∂μ, ∂β/∂α, have been calculated for a number of values of ɛ, μ, α, b/a, a/λ0, λ0 being the wavelength of a plane wave in the material occupying the part of the guide not occupied by gyromagnetic material. Comparisons are made with experimental losses measured by other authors; good agreement is found. The optimum design for Faradayrotation devices is discussed.

On the principle of stripline circulation

A circular disc of gyromagnetic material, when placed between two infinite plane conductors and magnetized axially, can support cylindrical modes having no field variation in the axial direction. In terms of a superposition of some of these (radiating) modes the physical principle of the stripline circulator can be explained, at least tentatively.Moreover, from this theory some information can be obtained about the dependence of physical dimensions (such as disc radius and stripline width) on frequency, magnetic bias field and magnetization. Reference is made to the eigen resonances of the ferrite disc. Some experimental results are given and compared with the theory.

Propagation in circular waveguides filled with gyromagnetic material

Using a specific form for the dependence of the permeability tensor components of a ferromagnetic medium on frequency and magnetizing field, the characteristic equation for the propagation constant in circular waveguide is written down. A method for discussing the complete mode spectrum of this equation is outlined. The general behavior of the spectrum is discussed.