Studies On The Micro-structure And Magnetic Properties Of Cr Substituted Co_xFe_3-xO₄ Ferrite 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 is 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 Co_xFe_3-xO₄(x=0.2-1.0) and Cr substituted nanocrystalline powders were prepared by chemical coprecipitation route, The powder samples were characterized by x-ray difrractometry(XRD) and vibrating sample magnetometry (VSM). We discussed the structure and magnetic properties of the samples. The main results were as follows:1. Structure phase transition and magnetic properties of the Co_xFe_3-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), Co_xFe_3-xO₄ phase and α-Fe₂O₃ phase were obtained at the same time. The specific saturation magnetization can be improved by properly increasing the cobalt content,2. Magnetic properties can be improved by properly reducing cobalt content. The specific saturation magnetization and coercivity for Co ferrites of low cobalt content y<0.4 are higher notably than series of high and middle cobalt content.During 1200°C...