Fe-B/FePt-type nanocomposite ribbons with high permanent magnetic properties

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 binary Fe50+xPt50-x (x = 0-20) ribbons spun at 45 m/s, followed by a 500 degrees C isothermal annealing, an ordered magnetically hard gamma(1) (FePt) phase can be fully formed at x <= 10, but the coercivity is merely of less than 2.0 kOe. Nevertheless, for ternary (Fe0.5+yPt0.5-y)(z)B100-z (y == 0-0.2; z = 82 and 84), multiple phases, namely gamma(1) Fe2B and Fe3B, with nanoscaled grain sizes (25-35 nm) can readily form in ribbons after an isothermal annealing at 500 degrees 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. A(i)H(c) of more than 12 kOe has been obtained in (Fe0.6Pt0.4)(82)B-18 (B-r = 6.6 kG, (BH)(max) = 8.9 MGOe), while a new record with a B-r of 9.4 kG, H-i(c) of 7.5 kOe and (BH)(max) of 14.0 MGOe can be achieved in (Fe0.675Pt0.325)(84)B-16. (c) 2004 Elsevier B.V. All rights reserved.