Magnetic properties of Sr-La system M-type ferrite fine particles prepared by controlling the chemical coprecipitation method

Single phase Sr-La M-type ferrite fine particles were prepared by the chemical coprecipitation and subsequent heat treatment methods. Optimum magnetic properties were achieved with materials of composition Sr/sub 0.794//sup 2+/La/sub 0.172//sup 3+/Fe/sub 0.335//sup 2+/Fe/sub 11 /./sub 74//sup 3+/O/sub 19/, and heat treatment of 950/spl deg/C/spl times/2 h in air, The magnetic and physical properties are /spl sigma//sub s/=90.5/spl times/10/sup -6/ Wb/spl middot/m/kg (72,0 emu/g), H/sub cJ/=505.3 kA/m (6.35 kOe), T/sub c/=454.4/spl deg/C, the lattice constants a=0.5882 nm, c=2.303 nm, the activation energy=230.9 kJ/mol (55.2 kcal/mol), and the average particle size=0.3 /spl mu/m.