2010 Volume 57 Issue 1 Pages 33-40
An experiment was carried out to investigate the effect of Nd2O3 substitution, molar ratio n {=Fe3+/(Co2++Ni2++Nd3+)}, concentration of alkali, inflowed time of alkali on the magnetic and physical properties of Co-Ni-Nd system spinel ferrite fine particles prepared by the chemical coprecipitation method without post-annealing. The chemical coprecipitation compositions were chosen according to the formula (CoO)0.5(NiO)0.5-x(Nd2O3)0.5x·n/2(Fe2O3), where x varied between 0 and 0.2 and n varied between 2.00 and 2.75. The typical magnetic properties were saturation magnetization σs=47.0×10-6 Wb·m/kg, residual magnetization σr=23.6×10-6 Wb·m/kg, coercivity HcJ =620.7 kA/m. To remove the superparamagnetic substance, the coprecipitation fine particles were etched with dilute sulfuric acid. As a result, in the (CoO)0.5(NiO)0.45(Nd2O3)0.025·1.25(Fe2O3) composition, when the excess NaOH and inflowed time were 1.1 mol and 1 s respectively, the following magnetic and physical properties were obtained: σs=75.1×10-6 Wb·m/kg, σr=56.7×10-6 Wb·m/kg, HcJ=861.8 kA/m, K1=3.56×105 J/m3, K2=-13.1×105 J/m3, and HA=3.90 MA/m.
