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

Abstract

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 Fe 50+ x Pt 50− x ( x=0–20) ribbons spun at 45 m/s, followed by a 500 °C isothermal annealing, an ordered magnetically hard γ 1 (FePt) phase can be fully formed at x⩽10, but the coercivity is merely of less than 2.0 kOe. Nevertheless, for ternary (Fe 0.5+ y Pt 0.5− y ) z B 100− z ( y=0–0.2; z=82 and 84), multiple phases, namely γ 1 , Fe 2B and Fe 3B, with nanoscaled grain sizes (25–35 nm) can readily form in ribbons after an isothermal annealing at 500 oC. 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 (Fe 0.6Pt 0.4) 82B 18 ( B r=6.6 kG, ( BH) max=8.9 MGOe), while a new record with a B r of 9.4 kG, i H c of 7.5 kOe and ( BH) max of 14.0 MGOe can be achieved in (Fe 0.675Pt 0.325) 84B 16.