Boosting coercivity of SrFe 12 O 19 nanocrystalline powders obtained by the citrate combustion synthesis method

: Strontium hexaferrite nanocrystalline powders are synthesized using a citrate combustion method and subsequently subjected to a post-synthesis processing aiming at tuning the micro-nanostructure for improving the magnetic properties. First, the synthesis thermal treatments are optimized in order to minimize the formation of secondary phases, mainly hematite. Second, the as-synthesized powders are conditioned by a two-step process: ball milling in wet medium (ethanol) and high-speed mixing. The final processed powders exhibit a saturation magnetization of 74 emu/g and a coercivity of 6450 Oe. Following a low-temperature combustion synthesis, the coercivity is one of the largest values reported for strontium ferrites. The combination of the two-step conditioning procedure results in a useful methodology to obtain SrFe 12 O 19 nanocrystalline powders with competitive properties. The morphological, structural and magnetic properties of the processed material make it a promising candidate for hard-soft ferrite-based composite magnets, where large coercivity values are highly desirable.

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