Effect of boron on the magnetic properties and exchange-coupling effect of FePtB-type nanocomposite ribbons

Abstract

Phase evolution and magnetic properties of melt-spun (Fe0.675Pt0.325)100−xBx (x=12–20) nanocomposite ribbons are investigated. For those ribbons spun at 45m∕s, followed with a 500°C isothermal annealing for 1–6h, the boron addition not only promotes disorder to order (γ→γ1) transformation but also leads to the formation of different kinds of Fe-borides. Pt exhibits a strong affinity to Fe during thermal processes in forming magnetically hard γ1(FePt) phase, leaving excess Fe to interact with B in forming Fe2B, Fe3B, or FeB. For x=12–18, all ribbons are composed of one hard phase, γ1-FePt, and three soft phases, γ-FePt, Fe2B, and Fe3B. But FeB also coexists for x=20. Through the exchange-coupling interaction between nanoscale γ1-FePt and multiple soft phases, record of magnetic properties of Br=9.4kG, Hci=7.5kOe, and (BH)max=14.0MGOe has been successfully developed in isotropic (Fe0.675Pt0.325)84B16 ribbons, where the reduced remanence ratio (σr∕σ12kOe) is as high as 0.86.

High hard magnetic properties and cellular structure of nanocomposite magnet Nd4.5Fe73.8B18.5Cr0.5Co1.5Nb1Cu0.2

“…For these remanence-enhanced materials, the studies on phase constitution of Fe 3 B/Nd 2 Fe 14 B [1,2], a-Fe(Co)/Nd 2 Fe 14 B, a-Fe/Pr 2 Fe 14 B [3][4][5][6] were reported. Recently, remanence enhancement was also observed in self-assembly FePt nanocomposite magnet [7] and in melt-spun FePtB magnets [8,9]. Theoretical works [10][11][12] have indicated that the magnetic properties of nanocomposite magnets strongly depend on microstructural parameters such as grain structure (grain size as well as homogeneity of grain distribution), phase components, phase volume fractions etc.…”

Crystallization processes and phase evolution in amorphous Fe–Pt–Nb–B alloys

“…In addition, the situation is more complicated due to the high boron content. In Fe-Pt-B alloys with off-stoichiometric Fe/Pt composition ratio [10] it has been shown that during annealing Pt exhibits strong affinity to Fe and forms the tetragonal phase, leaving the excess Fe to interact with B in forming borides such as Fe 3 B or Fe 2 B. Another important calorimetric event is represented by the endothermic peak at around 900 • C. This calorimetric event may be attributed to further phase transformation in the sample.…”

Magnetic and crystalline microstructures of Fe–B/FePt-type Nanocomposite ribbons with high permanent properties

“…[8,9], the magnetic properties of the ribbons were presented and discussed. The main results are summarized as follows: (1) For binary Fe 50+x Pt 50Àx (x ¼ 0 À 20) ribbons, an ordered magnetically hard g 1 -FePt phase can be fully formed at xp10; (2) For ternary (Fe 0.5+y Pt 0.5Ày ) z B 100Àz (y ¼ 0 À 0:2; z ¼ 82 and 84), the addition of B can effectively refine the grains; (3) strong exchange-coupling interaction between the nanoscale hard fct g 1 -FePt and the soft magnetic fcc g-FePt, Fe 2 B or Fe 3 B phases was proved by the Henkel plots of the (Fe 0.5+y Pt 0.5Ày ) z B 100Àz ribbons, giving rise to an improvement of not only the remanence B r but also the maximum energy product (BH) max ; (4) A new record of Fe-B/FePt-type nanocomposite ribbons with B r ¼ 0.94 T, j H c ¼ 600 kA/m and (BH) m ¼ 111.5 kJ/m 3 was obtained in (Fe 0.675 Pt 0.325 ) 84 B 16 ribbons.…”

“…In Ref. [8,9], the Fe-B/FePttype nanocomposite ribbons, Fe 50+x Pt 50Àx (x ¼ 0220), (Fe 0.5+y Pt 0.5Ày ) 82 B 18 (y ¼ 020:2) and (Fe 0.675 Pt 0.325 ) 100Àz B z (z ¼ 12220), were prepared by melt-spinning and the magnetic properties were investigated in detail. In Ref.…”