Hopkinson effect, structural and magnetic properties of M-type Sm3+-doped SrFe12O19 nanoparticles produced by a proteic sol-gel process

Samarium doped M-type strontium hexaferrites with chemical formula Sr1−xSmxFe12O19 (0≤x≤0.15) (SrM) were synthesized using the proteic sol-gel process. This low cost and environment friendly method yields easily reproducible magnetic powders. The crystal structure and phase purity were studied by X-ray diffraction (XRD). All the XRD patterns have been analyzed by Rietveld refinement technique using the P63/mmc space group which showed crystallite size in the nanoscale. Results of field emission scanning electron microscope show that the grains are regular hexagonal platelets. The saturation magnetization reaches a minimum at x=0.10 and increases at higher concentrations. The coercivity increases with Sm3+ concentration. The remarkable appearance of a Hopkinson peak at the M vs. T curve indicates that particles of the sample are composed of a single domain particles.