Magnetic properties of Mg-ferrite after milling process

An analysis of magnetic properties of powder of Mg-ferrite processed with a centrifugal mill was carried out. The starting ferrite powder was prepared by solid-state reaction at 1400 degreesC for 48 h. The powder:balls mass ratio was 1: 14, and the container and balls were made of agate. The crystalline size and internal strain were evaluated by XRD patterns using Williamson-Hall and Scherrer methods. The powders get a nanometric scale for low milling time. The X-ray study showed that after 17 h of milling peaks corresponding to alpha-Fe2O3 appear. The T-C were also evaluated by thermogravimetric analysis and correlate to crystalline size. Hysteresis curves are typical of soft magnetic materials with higher values of saturation magnetisation and lower coercivity. The starting sample has a saturation magnetisation of 39.2 emu/g and 0.4 Oe. At longer milling times, saturation magnetisation keeps nearly constant indicating the lack of inversion degree, while that coercivity increase up 576.7 Oe as a consequence of high density of internal stresses due to the mechanical grinding. (C) 2003 Elsevier Science B.V. All rights reserved.