Sol-Gel Synthesis of Mn-Sn-Ti-Substituted Strontium Hexaferrite Nanoparticles: Structural, Magnetic, and Reflection-Loss Properties

Substituted strontium hexaferrite nanoparticles with the chemical formula SrFe12-x (MnSn0.5Ti0.5) O-x/2(19)(x = 0-2.5, in a step of 0.5) were prepared by a sol-gel method. Phase identities and crystal structure of the synthesized nanoparticles were investigated by x-ray diffraction. The morphology of the nanopowders was determined by field emission scanning electron microscopy. Results obtained from Fourier-transform infrared spectroscopy revealed the presence of stretching and bending modes in the citrate complex. Mossbauer spectroscopy (M (S)) revealed occupancy of the hexagonal lattice structure by non-magnetic Mn2+ -Sn4+ -Ti4+ cations. Magnetic properties were measured by use of a vibrating sample magnetometer. The results showed that saturation magnetization and coercivity decreased with increasing x content. Microwave absorption properties were investigated by use of a vector network analyzer. It was found that the maximum reflection loss of substituted Sr-ferrite 1.6 mm thick reached -41.8 dB at a frequency of 4.3 GHz and a bandwidth of 7.5 GHz, with reflection loss being higher than -25 dB. These results imply that the prepared composites are good candidates for absorbers in the gigahertz frequency range.