Preparation And Studies Of Magnetic Properties Of High-performance Permanent Ferrite

Dure to its large uniaxial anisotropy, favorable performance/price ratio, higher Curie temperature and chemical stability, hexagonal Barium-Strontium ferrite with the magnetoplumbite(M) structure is one candidate of the most important magnetic materials used for permanent magnets and magnetic recording media. It is hard to improve their magnetic properties according to conventional process. In recent years, however, it has been recognized that LaCo or related substitution may lead to significantly improved ferrite magnets.A series of samples were produced by ceramic procedure method in this article. The samples of LaCo substituted SrM were prepared according to the formula La_xSr_1-xCo_xFe_2n-xO₁₉. Taking account of many practical situation, like "Sr losing" during preparation process, we set n for 5.8, and x for 0, 0.1, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6. The samples of Sm substituted SrM were produced according to the formula Sm_xSr_1-xFe_2nO₁₉. Here we set n for 5.6, and x for 0.05, 0.10, 0.15, 0.20. The work and conclusions of this article are as follows: 1.Investigation of LaCo substituted SrMâ‘  For x≤0.1, Tc≥1050℃, saturation magnetization increases more or less. â‘¡ For Tc≤1050℃, coercivity appears increasing tendency with increasing x;For Tc=1200℃, coercivity appears decreasing tendency.â‘¢Remanence ratio of the samples substituted by LaCo increases. For Tc= 1200℃ and x≤0.6, single phase samples with LaCo additives can be prepared by x-ray diffraction analysis. Lattice constants a stays constant and c is inclined to decreasing. 2.Investigarion of Sm substituted SrMâ‘  It appears decreasing tendency for saturation magnetization and remanent magnetization, but increasing tendency for coercivity with increasing x for Tc≤1250℃.â‘¡As the proportion Sr_1-xSm_xFe_11.2O₁₉, there are other phases in the samples prepared at different calcined temperature by x-ray diffraction analysis. So we mustchange the proportion if we want to obtain single phase ferrite.?For the samples of magnetic molding, their remanence ratio raises significantly based on increasing saturation magnetization and coercivity, so perfect materials can be prepared. 3.Effects of the squareness degree on the properties of magnetic materialsThe better are the permanent magnetic properties of the materials, the higher is squareness degree through comparison of the samples with different squareness degree.In a word, high performance permanent ferrite can be prepared chosing suitable mixture ratio and calcined temperature (or sintered temperature) by substituted SrM.