Magnetic properties of ferrites near ferromagnetic resonance in millimeter waves

Magnetic permeability and dielectric permittivity characteristics of barium and strontium ferrite materials in broad band millimeter wave frequency range have been obtained. The measurements have been done using free-space quasi-optical millimeter wave spectrometer in tunable magnetic field up to 8.5 kOe. A set of backward wave oscillators have been used as sources of high power coherent radiation tunable in 34 -120 GHz frequency range. Magneto-optical approach has been successfully employed for the separation of dielectric and magnetic effects in ferrites and simultaneous determination of complex dielectric permittivity and magnetic permeability of materials. Zone of strong absorption in the transmittance through the samples due to ferromagnetic resonance in millimeter waves has been observed. Shift of the ferromagnetic resonance to higher frequencies and broadening of the zone of strong absorption in transverse magnetic field have been observed. It has been shown that a variation in the chemical composition of ferrites leads to a change in the magnetic properties as well as absorption of materials in the millimeter wave range.