Comparative Study on Magnetic and Electromagnetic Behaviors of ZnFe₂O₄ and CoFe₂O₄ Nanoparticles Synthesized by Hydrothermal Method

We synthesized ZnFe₂O₄ and CoFe₂O₄ nanoparticles and investigated their magnetic and electromagnetic behaviors at room temperature. X-ray diffraction analyses indicated that these materials having average crystallite sizes of 22–31 nm, and their crystal structure belongs to the cubic-spinel class. While ZnFe₂O₄ exhibits soft magnetic behavior, with M_s = 88 emu/g and H_c = 130 Oe, CoFe₂O₄ exhibits hard magnetic behavior, with M_s = 65 emu/g and H_c = 620 Oe. Investigations into the complex permittivity and permeability dependent on the frequency (f) and thickness (t) revealed remarkable changes in their values at frequencies f = 12–16 GHz for both samples. In the range f = 13.5–13.8 GHz, reflection loss magnitudes of devices based on ZnFe₂O₄^– and CoFe₂O₄^– with t = 2.25–2.75 mm were about 11.3–14.2 dB, corresponding to electromagnetic wave absorption of 90–95%. Considering loss tangents, we found that both dielectric and magnetic losses contributed to the electromagnetic dissipation in the investigated materials.