Magnetic Properties and Microstructure of (Fe0.5+yPt0.5-y)zB100-z(y=0–0.2; z= 82 and 84) Melt Spun Ribbons Original Research Article

The Fe-B/FePt-type nanocomposite ribbons with strong exchange-coupling and high permanent magnetic properties have been developed by the melt-spinning method. For ternary (Fe0.5+yPt0.5-y)zB100-z (y=0–0.2; z=82 and 84), multiple phases, namely γ1, Fe2B and Fe3B, with nanoscaled grain sizes (25–35 nm) can readily form in ribbons after an isothermal annealing at 500 °C. Strong exchange-coupling between grains was found in these ribbons, giving rise to an enhancement of not only the remanence but also the maximum energy product. An iHc of more than 12 kOe has been obtained in (Fe0.6Pt0.4)82B18 (Br=6.6 kG, (BH)max=8.9 MGOe), and a Br of 9.4 kG, ft of 7.5 kOe and (BH)max of 14.0 MGOe can be achieved in (Fe0.675Pt0.325)84B16. Magnetically soft Fe2B and Fe3B were found to present in the matrix, as evidenced by high resolution transmission electron microscopy. Because of the higher saturation magnetization of Fe3B than Fe2B, the coexistence of Fe3B with Fe2B and γ1 phases was believed the main cause to result in the improved remanence and magnetic energy product of the (Fe0.675Pt0.325)84B16 ribbons.