Studies On The Structure And Magnetic Properties Of Co_xFe_3-xO₄ Ferrites And Their Al/Ce Substituted Nanoparticles

Research on magneto-optical storage is a very important branch in the field of magnetic information memory, the development of magneto-optical recording technology and materials are much significance for the progress of high capacity, density and erasable information recording technology. As the first generation magneto-optical recording material, TbFeCo has partly met the demands of market, but the antioxidation susceptibility of the rare-transitional subgroup elements is very poor, so it is a incipient fault for the information that inquire permanent preservation, besides, this material has limited the recording density for it can't work in the range of short wavelength, Therefore, it is urgent to explore the new generation of short-wavelength magneto-optical recording materials. Cobalt ferrite has been considered as attractive candidates for magneto-optical recording materials because of the good magnetic properties, chemical properties and Kerr effect in the range of 400-500nm wavelength.In this thesis, cobalt ferrites CoFe3-xO4(x=0.2-1.0) and Al/Ce substituted nanocrystalline powders were prepared by chemical coprecipitation route, The powder samples were characterized by x-ray diffractometry(XRD) and vibrating sample magnetometry (VSM). We dicussed the structure and magnetic properties of the samples. The main results were as follows:1. Structure phase transition and magnetic properties of the CoxFe3-xO4 were studied systematically. The experiment results show that the cobalt content has great influence on the sample structure, Monophase with a spinel structure were formed at high Co2+ content (x≥0.7), while at the lower Co2+ content (x<0.7), CoxFe3-xO4 phase and a-Fe2O3 phase were obtained at the same time. The specific saturation magnetization can be improved by properly increasing the cobalt content, the specific saturation magnetization in the range of x=0.6-1.0 notably higher than that of x<0.6, Higher as and Hccan be achieved simultaneously in the vicinity of x=1.0.2. The magnetic properties can be further improved by Al/Ce cation doping, for the Al substituted Co1.0Fe2-xAlxO4 (x=0.1-0.5) nanoparticles, the coercivity was slightly increased in the rang of x=0.1-0.3, For Co1.0Fe2-xCexO4(x=0.1-0.3), in the range of substistituted content x≤0.2, the coercivity was enhanced greatly while saturation magnetization didn't decline aimostly. So it is favorable for the material to putting into use in magneto-optical recording.