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

Abstract

Single phase Sr-La-Co M-type ferrite fine particles were prepared by the chemical coprecipitation and subsequent heat treatment. The chemical reagents used for an experiment are FeCl3·6H2O, Sr(NO3)2, La(NO3)3·6H2O, Co(NO3)2·6H2O and CoCl2·6H2O. The chemical coprecipitation composition were chosen according to the formula {(SrO)·n/2(Fe2O3)}100-x-y (La2O3)x(CoO)y, where n was fixed at 7.0 and x at 1.5 and y was varied between 1.0 and 10.0. A water solution containing Sr2+, Fe3+, La3+ and Co2+ was poured into solution of NaOH (pH=13.0). Aqueous suspensions containing the coprecipitated products were boiled for 2h, and they were carefully washed, filtrated and dried at 80°C for 12h. The obtained fine particles were heated 950 to 1100°C for 2h in air to get single phase Sr-La-Co M-type ferrite fine particles. The conditions determined as optimum for preparing the fine particles with the best values of σs = 90.2 × 10-6 Wb·m/kg (71.8emu/g), σr = 45.1 × 10-6 Wb·m/kg (35.9emu/g), HcJ = 525.2kA/m (6.60kOe) and Tc = 453.9°C are as follows: composition; Sr2+0.812La3+0.045Co2+0.045 Fe3+9.236O2-19; heat treatment; 1000°C × 2h in air; the average particle size; 0.3-0.4 μm.