Magnetic properties of randomly oriented BaM, SrM, Co 2Y, Co 2Z and Co 2W hexagonal ferrite fibres

The microstructure and magnetic properties of randomly oriented BaFe12O19, SrFe12O19, Ba2Co2Fe12O22, Ba3Co2Fe24O41, Ba3Ca0.3Co2Fe24O41 and BaCo2Fe16O27 hexaferrite fibres were characterised. 2D and 3D AFM and MFM images were taken of a single BaM fibre. Magnetic properties of random ferrite fibres compared well to expected values for polycrystalline ceramics. The little-characterised Co2W ferrite was found to have M s and H c similar to that of Co2Z. Relatively small applied fields of <0.05T were required to reverse the magnetisation of all the soft hexaplana ferrite fibres, and all had H c<40kA/m, becoming demagnetised in fields <0.025T. Random Co2W fibres had a high M r/M s ratio of 0.56, (greater than M ferrites), despite being very magnetically soft (low coercivity), due to the unusual "lobed" shape of their hysteresis loop, which was attributed to their fibrous nature, and elongated growth of the grains along the fibre axis. Co2Z had the lowest H c of all the ferroxplana fibres. © 2011 Elsevier Ltd.