TREATMENT OF STRONTIUM HEXAFERRITE POWDER SYNTHESIZED CONVENTIONALLY TO PRODUCE HIGH COERCIVITY

Strontium hexaferrite powder, produced conventionally from strontium c arbonate and iron oxide has been treated in nitrogen and hydrogen atmo spheres and then calcined in air. Magnetic measurements after the gas treatment stage indicated a marked decrease of intrinsic coercivity En d an increase in saturation magnetisation. During the calcination stag e there was a recovery oi the magnetic properties. The material now ex hibited a remanence and saturation magnetisation close to that of the starting hexaferrite, but a very much higher intrinsic coercivity. The highest coercivity obtained was around 400 kA/m, which is very high f or a hexaferrite powder, particularly one synthesized conventionally, without extenive milling. The high coercivity was attributed to a much finer grain size.