Nano Ferrites Microwave Complex Permeability and Permittivity Measurements by T/R Technique in Waveguide

There is a huge demand to accurately determine the magnetoelectrical properties of particles in the nano-sized regime due to the modern IC technology revolution and biomedical applications. In this paper, we present a microwave waveguide measurement technique for measuring complex permeability and permittivity of expensive nano-sized magnetic powder materials. We used a vector network analyzer to provide a standard TRL calibration for free space inside waveguide measurements. In order to maintain the recommended insertion phase range, a very thin prepared sample was loaded inside the calibrated waveguide. The loaded material´s magnetic and dielectric effects were also considered in the cutoff wavelength calculation of the propagation constant of the TE₁₀ wave from the geometrical dimensions of the waveguides. These provisions make the permeability and permittivity measurements more reliable than those found by commonly used techniques. We used six different compounds of nano-sized ferrite powders (Fe₃O₄, CuFe₂O₄, CuFe₂O₄Zn, F₁₂NiO₃Zn, BaFe₁₂O₁₉, and SrFe₁₂O₁₉), in which the average diameter of nano particles is less than 40 nm, for measurement purposes. We measured the complex permeability and permittivity from 3.95 to 5.85 GHz. The results show that the dielectric permittivity of these materials is quite different from that of solid-state materials.