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

Abstract

An amorphous phase was formed for (Fe 0:75 Pt 0:25 ) 100Àx B x (x ¼ 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 1 -FePt (fct), Fe 2 B and -FePt (fcc) phases, and their average grain sizes were about 15 nm after annealing at 785 K for 900 s. The remanence (B r ), reduced remanence (M r =M s ), coercivity (iH c ) and maximum energy product ðBHÞ max were 0.96 T, 0.83, 340 kA/m and 102.2 kJ/m 3 , respectively, for the 25 at%B alloy, and 0.91 T, 0.82, 368 kA/m and 96.5 kJ/m 3 , 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 1 -FePt and soft Fe 2 B and -FePt magnetic phases.

Preparation of Fe–Pt–Si Amorphous Ribbons and Their Coercivity after Crystallization

“…1. [3][4][5][6][8][9][10][11][12][13] In Fig. 1 , the amorphous-forming ability of the alloys becomes low, and it seems difficult to obtain an amorphous phase for near equiatomic Fe-Pt alloys with a B content higher than 20 at%, as determined from Fig.…”

“…The grain size is almost the same as that of the L1 0 FePt phase in Fe-Pt-B ternary ribbons with hard magneticity. 5,6) …”

“…3,4) Recently, it was reported that Fe-Pt-B amorphous ribbons were successfully obtained by melt-spinning and that high saturation and residual magnetic flux density (B s and B r , respectively) can be achieved by nanocrystallization of the amorphous meltspun ribbons. [5][6][7] The phases found in the ternary Fe-Pt-B as-spun ribbons are summarized in Fig. 1.…”

The Effect of Pt Addition on the Structure and Magnetic Properties of Melt-Spun Fe_80–xPt_xB₂₀ Alloys

“…In addition, for extension of application fields, it is also important to further reduce Pt content without detriment to the hard magnetic properties for the Fe-Pt-B magnets. We have investigated the effects of Pt and B concentration on the structure and magnetic properties of melt-spun Fe-Pt-B alloys with Pt concentration of over 20 at.% [1,5]. However, little is known about the effects of smaller amount of Pt content on the structure and magnetic properties of Fe-Pt-B alloys.…”

Magnetic properties and structure of Fe–Pt–M–B (M=Zr, Nb and Ti) alloys produced by quenching technique

“…A nanocomposite structure consisting of L1 0 -FePt, fcc-Fe and Fe 2 B was obtained after annealing [8,9] of transition metals (M = Zr, Nb and Ti) and B to near-equiatomic FePt alloys on melting (T m ) and order-disorder transformation (T tr ) temperatures. These transition elements have larger atomic radii [10] than Fe and Pt and exhibit large negative mixing enthalpy between Pt [11], as shown in Table 1.…”