To demonstrate the potential of nuclear magnetic resonance (NMR) spectroscopy for investigating detailed structural properties in ferromagnetic materials, three different particle sized cobalt (Co) powders have been ball milled for 24 h are accurately characterised by internal-field Co-59 NMR. The Co-59 NMR spectra show distinct resonance bands corresponding to the different Co sites. face-centred-cubic (fcc), hexagonal-close-packed (hcp) and stacking faults (sfs), in Co metal powders. The hcp+fcc-->hcp phase transition encouraged by ball-milling was observed and quantitative values for each Co environment were obtained. (C) 2008 Elsevier Inc. All rights reserved.