Boosting the coercivity of SrFe12O19 nanocrystalline powders obtained using the citrate combustion synthesis method

Abstract

Abstract Strontium hexaferrite nanocrystalline powders were synthesized using a citrate combustion method and subsequently subjected to post-synthesis processing with the aim of tuning the micro-nanostructure to improve the magnetic properties. Firstly, the synthesis thermal treatments were optimized in order to minimize the formation of secondary phases, mainly hematite. Secondly, the as-synthesized powders were conditioned by a two-step process: ball milling in wet medium (ethanol) and high-speed mixing. The final processed powders exhibited a saturation magnetization of 74 emu g−1 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 SrFe12O19 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.