The effects of dry-milling BaFe12O19 in air for periods of 190, 360, 5
90, 690 and 1000 h have been investigated by X-ray diffraction and Mos
sbauer effect measurements. The sizes of the BaFe12O19 particles decre
ase on milling, as expected, although a partial decomposition of BaFe1
2O19 to alpha-Fe2O3 is found to rake place on extended milling (1000 h
). The room temperature Mossbauer spectra are consistent with superpar
amagnetic relaxation associated with the fine BaFe12O19 and alpha-Fe2O
3 particles. The X-ray diffraction patterns of all the milled samples
exhibit features indicative of a disordered structural state, consiste
nt with the nanoscale particles and a nanostructured state.