To enhance the magnetic properties of ferrite powders, it is critical to control their compositions and morphologies. In particular, composite sheets containing ferrite powders for EM absorbers and magnetic sensors require homogeneous single crystal ferrite powders to obtain the tunable properties. In this experiment, Mn substituted strontium ferrite powders for high coercivity were synthesized by the molten salt method to control their morphology and structure. As a result, single crystalline hexa-ferrite powders with an average size of 1∼3 μm were successfully obtained by initial calcination at 850°C for 1 hr and then at 950°C for 1 hr and subsequent calcination at 1050°C for 0.5 hr. These synthesized powders were revealed to have a magnetic saturation of 72.6 emu/g and a coercivity of 4019 Oe.

The doping element and morphology are important factors for improving the magnetic properties of M-type hexaferrite powder. As the demand for electromagnetic absorber and magnetic sensors increases in the market, it is required to develop hexaferrite powder with a homogenous shape and excellent magnetic properties. In this study, Ca substituted strontium hexaferrite powders were synthesized by the molten salt method under various calcination conditions. The morphology and magnetic properties of the synthesized powders were successfully controlled according to the Ca content and calcination conditions. As a result, single-crystalline Sr0.90Ca0.10Fe12O19 powders with an average thickness of 0.4 µm were successfully obtained by calcining at 950 °C for 1 h. The synthesized powders had a magnetic saturation of 74.9 emu/g and a coercivity of 3397 Oe.

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