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In this research, nano-sized powders of Zr-Mn substituted strontium hexaferrite (Sr(Zr,Mn) x Fe 12−2x O 19 (x = 0, 2, 2.5, 3)) were synthesized by sol-gel auto-combustion route using subsequent heat treatment. The samples were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), Mössbauer spectroscopy and vibration sample magnetometer (VSM) techniques. XRD and Mössbauer spectroscopy results revealed formation of Sr(Zr,Mn) x Fe 12−2x O 19 accompanied with Mn δ Fe 2−δ O 4 lateral phase in the samples. Also, FTIR and XRD results demonstrated presence of SrO impurity phase. FESEM micrographs show particle size reduction and presence of two distinct powder morphologies with different brightness levels with Zr 4+ and Mn 2+ substitutions which approves existence of lateral phases in the substituted samples. TEM micrographs show nanometric particles with sizes smaller than 100 nm with high crystallinity. Mössbauer results showed that at low level of substitution, Zr 4+ ions prefer to occupy both 4f1 and 2b however, at higher level of substitution, they prefer exclusively 4f1 site. While, Mn 2+ ions distributed approximately equally between 12k and 2a sites. The presence of nonmagnetic Zr 4+ cation leads to decrease in exchange interaction, especially at 12k and 2a sites. VSM results showed decrement of coercivity force (i H c) from 5593.60 to 3282.46 Oe and maximum magnetization from 62.60 to 46.15 emu g −1 , respectively, by increment of Zr-Mn substitution values. Variations in maximum magnetization magnitude have been explained on the basis of occupation of the substituted cations at different iron sites.

In this research, nano-sized powders of strontium hexaferrite were synthesized by sol-gel auto-combustion route using stoichiometric ratio of Fe/Sr. The effect cetyltrimethylammonium bromide (CTAB) addition on microstructure and magnetic properties of hexaferrite have been studied. The samples were characterized using X-ray diffraction (XRD), dynamic light scattering (DLS), vibration sample magnetometer (VSM), field emission scanning electron microscope (FESEM), and transmission electron microscope (TEM) techniques. The results revealed that CTAB addition causes a noticeable reduction in the amount of residual α-Fe 2 O 3 phase, since presence of CTAB in the sol facilitates the entrance of Sr 2+ ions into the reactions of hexaferrite formation. Also, the morphology of the particles was affected by CTAB addition. Irregular-shaped nanoparticles were synthesized without CTAB additions, while platelet-shaped nanoparticles were obtained by CTAB addition. The mechanism of strontium hexaferrite nanopowder formation has been explained. Magnetic measurements in the sample calcined at 800°C for 1 h represented that CTAB addition increased the coercivity force ( i H c ) from 4.9 to 5.2 kOe and maximum magnetization (M max ) from 48.4 to 60.4 emu/g, respectively.The online version of the original article can be found at http:// dx