Magnetic, elastic, dielectric, microwave absorption and optical characterization of cobalt-substituted nickel spinel ferrites

Magnetic, elastic, dielectric, microwave absorption and optical properties of nickel cobalt ferrites =Ni1-xCoxFe2O4 (x 0.0, 0.15, 0.30, 0.45, 0.60, 0.75, 0.90, 1.0) synthesized using Pechini's sol-gel method are investigated. Saturation magnetization, coercivity and Curie temperature increased with doping of cobalt. An optimized combination of high M-S (86.12 emu g(-1)) and lower coercivity (694.7 Oe) was obtained for composition NC 0.90. Curie temperature increased from 602 degrees C to 705 degrees C as amount of Co increased from 0.0 to 1.0. In FT-IR spectrum, characteristic absorption bands were observed in 400-600 cm(-1) range. Impedance analyzer was used to determine dielectric and impedance properties in 20 Hz-120 MHz frequency range. The prepared ferrites were evaluated for their applications in 12.4-18 GHz frequency band using vector network analyzer (VNA). Minimum reflection loss of -44.48 dB at 15.74 GHz frequency was obtained for composition NC 0.90. Optical spectra at excitation wavelength of 350 nm show sharp peaks around 330 nm in all the compositions.