Magnetic Properties of Sr-M Ferrite Fine Particles

Abstract
Single phase Sr-M ferrite fine particles were prepared by the chemical coprecipitation and subsequent heat-treatment methods. The chemical reagents used for an experiment are FeCl₃ · 6H₂O and Sr(NO₃)₂. A solution containing Fe³⁺ and Sr²⁺ in the molar ratio (Fe³⁺/Sr²⁺ = n)7.0~11.0 was poured into a solution of NaOH (pH = 10~13). Aqueous suspensions containing the precipitated products were boiled for 2hs, and they were carefully washed, filtrated and dried at 80 °C for 8hs. The obtained fine particles were heated 800 to 1100 °C for 2hs in air to get single phase Sr-M ferrite fine particles. The optimum preparing condition of single phase Sr-M ferrite fine particles are as follows : reagents : FeCl₃ · 6H₂O and Sr(NO₃)₂ : the molar ratio : Fe³⁺/Sr²⁺= 8 ; pH= 13 ; the heat-treatment condition : 900°C x 2hs in air. The magnetic and physical properties are σ_s=87.0x10^-6, H_Cl = 501.3 kA/m (6.3 kOe), H_Aave = 945.4 kA/m (11.9 kOe), Tc = 462 °C. The lattice constants a = 5.882 x 10^-10 m, c = 23.05 x 10^-10m. c/a=3.919, the activation energy = 182.0 kJ/mol (43.5 kcal/mol) and the average particle size = 0.2 µm.