Magnetic properties of isotropic SrFe12O19 fine particles prepared by mechanical alloying

M-type Sr-hexaferrites fine particles have been prepared by mechanical alloying. The influences of milling conditions on magnetic properties of SrFe12O19 compounds have been systematically investigated. It can be found that annealing treatment at low temperature can play similar role in structural transformation as compared with long time milling process. For those samples annealed at about 750-800 degrees C, it is clear that saturation magnetization sigma(s), values are more sensitive to milling conditions than coercivity values H-c. The maximum sigma(s) of 74.8 emu/g and H-c of 5.6 kOe have been obtained in the isotropic powders annealed at 1000 degrees C after milling for 30 h by using high energy mill. With prolonged annealing time, little changes of magnetic saturation and coercivity in powders can be observed and short annealing time results in low properties. The coercive field H-c, as determined from demagnetization curve, corresponds to the pinning or nucleation field. (C) 1998 Elsevier Science B.V. All rights reserved.