Materials Transactions Online

Materials Transactions, Vol.46 No.04 (2005) pp.891-894
© 2005 The Japan Institute of Metals

Formation, Crystallized Structure and Magnetic Properties of Fe--Pt--B Amorphous Alloys

Akihisa Inoue1, Wei Zhang1,2,, Takako Tsurui1 and Dmitri V. Louzguine1

1Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
2Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Sendai 980-8577, Japan

An amorphous phase was formed for (Fe0.75Pt0.25)100-xBx (x=25 and 30) alloys by melt-spinning. Their crystallization temperature were 671 and 667 K, respectively. The amorphous alloys exhibited good soft magnetic properties. The crystallized structure consisted of γ1-FePt (fct), Fe2B and γ-FePt (fcc) phases, and their average grain sizes were about 15 nm after annealing at 785 K for 900 s. The remanence (Br), reduced remanence (Mr/Ms), coercivity (iHc) and maximum energy product (BH)max were 0.96 T, 0.83, 340 kA/m and 102.2 kJ/m3, respectively, for the 25 at%B alloy, and 0.91 T, 0.82, 368 kA/m and 96.5 kJ/m3, respectively, for the 30 at%B alloy. The reversible demagnetization loop behavior was also confirmed. Consequently, the good hard magnetic properties are interpreted as resulting from exchange magnetic coupling among nanoscale hard γ1-FePt and soft Fe2B and γ-FePt magnetic phases.

(Received 2004/12/27; Accepted 2005/3/14; Published 2005/4/15)

Keywords: iron-platinum-boron alloy, melt-spun, amorphous, crystallized structure, nanocomposite permanent magnet

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