Investigation of structural and magnetic properties of nanocrystalline Mn-doped SrFe12O19 prepared by proteic sol-gel process

Nanoparticles of SrFe(12-x)Mn(x)O19 (x=0.0 and 0.10) were synthesized by a proteic sol-gel process. Thermogravimetric and differential thermal analyses (TG-DTA) indicated the formation of nanocrystalline strontium ferrite phase at a calcination temperature of 1000 degrees C. Structural and microstructural evolutions of the samples were studied by X-ray powder diffraction (XRD) and the Rietveld method. XRD patterns demonstrated that all samples consisted of single-phase M-type strontium hexaferrite. The crystal lattice constant did not change significantly with manganese substitution, ranging from 0.5877(3) nm (x=0.0) to 0.5876(3) nm (x=1.0). In addition, the average crystallite size, which was determined from the Williamson-Hall formula, was about 464-52.6 nm. Infrared spectroscopy (FT-IR) showed the presence of three principal absorption bands in the frequency ranges around 435-535 cm(-1) and around 595 cm I, indicating the formation of the hexaferrite. Scanning electron microscopy (SEM) revealed that particles consisted of irregular platelets with sizes from 68 to 204 nm. Room-temperature Mossbauer investigations revealed that manganese ions preferentially occupied the 12k, 4f(1), 4f(2), and 2a sites. Hysteresis loops (M-H) showed that the saturation magnetization, remanence, and coercivity decreased with manganese doping. This effect is discussed in terms of the distribution of metal cations in the tetrahedral and octahedral sites. (c) 2015 Elsevier B.V. All rights reserved