No abstract

Given the huge and increasing global demand for permanent magnet supply, even slight improvements of the magnetic properties and cost effectiveness of permanent magnet materials could incur huge energy and money savings. This article is concerned with the optimization of the experimental conditions for the production of pure M-type BaxSr1−xFe12O19 hexaferrites with improved magnetic properties. X-ray diffraction analysis revealed the formation of a single M-type hexaferrite in the ball milling route at a sintering temperature of 1100 °C for the samples with x = 0.0 and 0.5, and at 1200 °C for x = 1.0. In the sol–gel route, however, a single M-type phase was successfully synthesized at a significantly lower temperature of 890 °C. The magnetic parameters of the samples prepared by ball milling exhibited an improvement at lower Ba contents. On the other hand, the samples prepared by sol–gel method exhibited a significant improvement of the intrinsic coercivity (HcM) compared with those prepared by ball milling, with the highest value of 5.9 kOe observed at x= 0.0 and sintering temperature of 1000 °C. The saturation and remnant magnetization, however, were not influenced significantly by the synthesis route, and remained relatively high, comparable with the best parameters for ferrite isotropic magnets. The sample with x = 1.0 prepared by sol–gel method and sintering at 890 °C exhibited the highest residual induction Br = 2509 G, practical coercivity HcB = 1919 Oe, and maximum energy product (BH)max = 9.9 kJ m−3.

No abstract

No abstract

We report on the synthesis and characterization of Ba3[Cu0.8−xZnxMn0.2]2Fe24O41 (x = 0.0, 0.2, 0.4, 0.6, and 0.8) barium hexaferrites. The samples were prepared by high-energy ball-milling technique and double-sintering approach. The effects of Zn substitution for Cu on the structural and magnetic properties of the prepared samples were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). XRD patterns of the samples revealed the presence of a major Z-type hexaferrite phase, together with secondary M-type and Y-type phases. The magnetic results indicated that the saturation magnetization increased slightly with increasing the Zn content, while the coercivity and magnetocrystalline anisotropy field exhibited a decreasing tendency with the increase of Zn content. The thermomagnetic curves revealed the complex magnetic structure of the prepared samples and confirmed that the Curie temperature of the magnetic phases decreased with increasing x as a result of the reduction of the strength of the superexchange interactions.