LAUSR

Superparamagnetic particles of Ni ferrite prepared by co-precipitation technique were mixed with epoxy and studied by broadband ferromagnetic resonance (BFMR) in the range 2–26 GHz. The XRD and TEM showed that particles had a spinel structure and a small size around 27 nm. The particles exhibited a hysteresis loop with superparamagnetic behavior and the moment-temperature analyses showed a blocking temperature higher than room temperature. SC-BFMR analysis was based on measuring the diode voltage ratio when the sample is over the SC to the diode voltage when the sample is absent. The BFMR spectrums of Ni ferrite-epoxy composites were more refined at low fields than the higher one, when different phenomena were interfered. Below 5000 G, the resonant frequency-field relation was linear for all samples. The effective g-factor and effective magnetization calculated from resonant frequency field were generally decreased as Ni2+ was increased. The losses were represented as the inverse of the quality factor which was increased with Ni2+ content and was dropped as frequency was growing.