Optimum preparation conditions of Fe-deficient Ca-based M-type ferrite

摘要

??We investigated synthesis conditions and magnetic properties of Fe-deficient Ca-based hexagonal ferrites, Ca_(1?x )La_(x )Fe_(y )O_(19?σ ) (x = 0.1–0.3, y = 2.0–10), and found the formation of M-type ferrite at x = 0.1–0.3 and y = 7.0–9.0 above 1200°C. Samples of y = 2.0–6.0 showed deviation from the initial compositions since molten calcium-rich oxide (possibly CaFe_(2)O_(4)) leaked out from the samples above 1200°C. The X-ray diffraction pattern of Ca_(0.8)La_(0.2)Fe_(8.0)O_(19?σ ) sintered at 1250°C demonstrates the single phase of M-type hexagonal ferrite. The saturation magnetization of this sample was 68.0 Am~(2)/kg at room temperature and its Curie temperature was about 400°C, which is slightly lower than that of the Sr-based M-type ferrite (460°C).