Studies On Magnetic Properties Of Substituted Sr Hexaferrite Nanoparticles

M-type hexaferrite has become an important functional materials for it's high coercive ,perfect microwave properties and good performance/price ratio. Recently, M-type hexaferrite have been considered as attractive candidates for high-density recording materials because of the good mechanic, chemical properties and high magnetic anisotropy.In this thesis, LaCo doped Strontium ferrite nanoparticles were prepared by chemical sol-gel route. LaZn doped Strontium ferrite nanoparticles were prepared by chemical coprecipitation method. The samples were characterized by x-ray diffractometry(XRD) and vibrating sample magnetometry (VSM). We discussed the structure and magnetic properties of the samples. The main results were as follows:1.The results of phase transition of Sr0.8La0.2Fe11.8Co0.2O19 indicated that γ-Fe2O3 phase was formed below annealing temperature 500℃. antiferromagnetic ferrite SrFe2O4 can be observed at temperature 550℃, and magnetoplumbite phase (M phase) at temperature 650℃. The samples were single phase up to x=0.3 at the annealing temperature 850℃. For x≥0.4, Secondary CoFe2O4 and LaFeO3 phase were detected in weak proportions at the same temperature.The experimental results showed that for an amount of substitution(x=0~0.2), the sesidual magnetic induction Br increased and coercive strength Hc increased too. The maximum of Hc appeared at x=0.2. So this substitution was benefit for permanent-magnet performance.2.For LaZn doped Strontium ferrite nanoparticles ,When the amount of substituion 0≤x≤0.3, The substituion ferrites showed higher values of saturation magnetization σs than unsubstituion. Compared with the annealing temperature 970℃, 1000℃ and 1030℃, the σs of 1000℃　was best ,and the maximum value of σs was 64emu/g who appeared at x=0.1. coercive strength Hc decreased when 0