Structural, Magnetic, and Microwave-Absorption Properties of Nanocrystalline Ca(MnSn) x Fe12-2x O19 Ferrites

Nanoparticles of Ca(MnSn) (x) Fe12-2x O-19 with x ranging from 0.00 to 0.6 in steps of 0.2 were prepared by use of the citrate precursor method. The structural, microwave-absorption, and magnetic properties of these ferrites were determined by use of different characterization techniques. The morphology of the ferrite powders was investigated by transmission electron microscopy (TEM). X-ray diffraction (XRD) was used for structural and micro-structural studies, and revealed that the samples had an M-type hexagonal structure. The crystallite size for each sample was calculated by use of the Scherrer formula for the most intense peak (411) and the results were compared with those obtained from TEM images of the samples. The particle size of the powder varied from 60 to 36 nm. Magnetic measurements were performed by vibrating sample magnetometry (VSM) at room temperature. The microwave-absorption properties of ferrite (70 wt.%)-polymer (30 wt.%) composites 2 mm thick were investigated by vector network analysis (VNA) in the frequency range 12-20 GHz. The ferrite for which x = 0.4 had a minimum reflection loss of -29 dB at 17.3 GHz with a -15 dB bandwidth over the extended frequency ranges 12.9-14.5 GHz and 16.7-18 GHz. The minimum loss reached -32 dB at frequency of 17 GHz when the total amount of Mn2+ and Sn4+ ions was 0.6. These results suggest that the synthesized magnetic composites can be used as effective microwave absorbers in military applications (radar cross-section reduction).