The authors dould like to thank J.Ormerod and E.Rozendaa1 of Mullard Magnetic Components for their cooperation and the provision of the magnets and G.Cliffe of the Department of Metallurgy;
University Manchester for his help dith TEM and X-ray microanalysis. This dork nTas supported by the UK Science and Engineering Research Council and the Concerted European Action on Magnets programme (CEAM) of the European Community Stimulation Action;