Magnetic properties of Ba-Nd-Co system M-type ferrite fine particles prepared by controlling the chemical coprecipitation method

Single phase Ba-Nd-Co M-type ferrite fine particles were prepared by the chemical coprecipitation method and subsequent heat treatment method. Optimum magnetic properties were achieved with materials of composition Ba2+0.99 Nd3+0.118 Co2+0.041 Fe3+11.86 O2−19 and heat treatment of 1000°C×2 h in air. The magnetic and physical properties are σs=80.7×10-6 Wb m/kg(64.2 emu/g), HcJ=479.2kA/m(5.99 kOe), Tc=452∘C, the lattice constants a=0.5889nm, c=2.318nm, the activation energy = 295.3 kJ/mol(70.31 kcal/mol), and the average particle size = 0.15 μm. Temperature coefficient of the intrinsic coercivity (0.07%/°C) of these powder were found to be very small.