JOURNAL OF ALLOYS AND COMPOUNDS, cilt.660, ss.324-335, 2016 (SCI İndekslerine Giren Dergi)
Mn-Co substituted spinel Ni-Zn ferrite nanoparticles were synthesized in the form of NixZn0,8-xMn0.1Co0.1Fe2O4 (0 <= x <= 0.8) using the solid state reaction route. 1 wt.% B2O3 (boron) was added to initial mixture to inhibit crystal growth. Structural characterization showed that single phase NiZn-ferrite nanoparticles were obtained upto the nickel concentration of x = 0.5 and above that a small fraction of hematite phase (alpha-Fe2O3) was detected. It was observed that ac conductivity of nanoparticles decreases with increasing nickel amount giving rise to better stability of electrical bonds between Ni and Fe ions. Besides, ac conductivity also decreases with decreasing frequency which is considered as a signature of an ionic conductivity. Magnetic measurements revealed that as nickel concentration increases up to x = 0.5, the saturation magnetization of the samples increases. Further increase results in a decrease in the magnetization. The microwave characterization showed that the samples of Ni0.6Zn0.2Mn0.1Co0.1Fe2O4 and Ni0.8Mn0.1Co0.1Fe2O4, have the best absorption properties with minimum reflection losses of -25 dB at 10 GHz and 12 GHz, respectively. The mechanism of absorption appears to be quarter wavelength cancellation at the matching thickness, which increases exponentially with decreasing microwave frequency. (C) 2015 Elsevier B.V. All rights reserved.