Structural Heterogeneity of the Melt-spun (Fe, Co)-Si-B-P-Cu Alloy with Excellent Soft Magnetic Properties

AbstractA structural heterogeneity of a newly developed soft magnetic Fe81.2Co4Si0.5B9.5P4Cu0.8 melt-spun alloy has been studied by transmission electron microscopy (TEM) and electron diffraction. Hollow-cone dark-field TEM imaging revealed that the density of coherent scattering regions in the as-quenched Fe81.2Co4Si0.5B9.5P4Cu0.8 alloy is as high as that in the Fe85.2Si2B8P4Cu0.8 hetero-amorphous alloy (NANOMET®). According to the aberration-corrected high-resolution TEM, crystalline atomic clusters, typically of ∼1nm in diameter, are densely distributed in an amorphous matrix of Fe81.2Co4Si0.5B9.5P4Cu0.8 alloy, while nanobeam electron diffraction detected weak Bragg reflections from Fe clusters with the body centered cubic structure. These results unambiguously reveal structural heterogeneity of the as-quenched Fe81.2Co4Si0.5B9.5P4Cu0.8 alloy, which is similar to that observed in the NANOMET®

Direct imaging of structural heterogeneity of the melt-spun Fe₈₅.₂Si₂B₈P₄Cu₀.₈ alloy

A structural heterogeneity of the melt-spun Fe₈₅.₂Si₂B₈P₄Cu₀.₈ alloy has been studied by spherical aberration (Cs) corrected high-resolution transmission electron microscopy. Hollow-cone illumination imaging revealed that the density of coherent scattering regions in the as-quenched Fe₈₅.₂Si₂B₈P₄Cu₀.₈ alloy is much higher than that in the Fe76Si9B10P5 bulk metallic glass. According to the Cs-corrected TEM, crystalline atomic clusters, typically of ∼1 nm in diameter, are densely distributed in an amorphous matrix of Fe₈₅.₂Si₂B₈P₄Cu₀.₈ alloy. Observation of four-fold and six-fold atomic arrangements of these clusters implies existence of Fe clusters with the body centered cubic structure. These Fe clusters must be responsible for the formation of ultrahigh-density α-Fe nanocrystals produced by post-annealing.Kazuhisa Sato, Kana Takenaka, Akihiro Makino, and Yoshihiko Hirotsu, "Direct imaging of structural heterogeneity of the melt-spun Fe₈₅.₂Si₂B₈P₄Cu₀.₈ alloy", AIP Advances 5, 067166 (2015) https://doi.org/10.1063/1.4923329

Ordering of island-like FePt crystallites with orientations

Thin films of oriented island-like crystallites of L10 FePt separated by amorphous (a-) Al₂O₃ were fabricated. The process took advantage of the overgrowth of α-Fe on Pt "seed" particles epitaxially grown on (100) NaCl and MgO substrates and the ordering reaction between Fe and Pt upon annealing at temperatures higher than 500°C. The coercivities of the annealed (600°C for 6 h) a-Al₂O₃/Fe(1 nm)/Pt (1.5 nm) films on both the NaCl (100) and MgO (100) substrates are higher than 3.3 kOe. Transmission electron microscopy observation showed that the film consisted of oriented L10 FePt island-like crystals with an average size of 12 nm and a separation of 4 nm. It was found that any one of the three 〈100〉 axes of the fcc Pt parent particles could act as the tetragonal c axis of the L10 FePt superstructure and all three-variant ordered crystalline domains of the tetragonal L10 phase could exist in the small 10-nm-size FePt crystallites. The high magnetic coercivity of the film, with well-separated FePt particles, can be attributed to the ordering (L10) as well as the oriented nature of the FePt crystallites. © 1999 American Institute of Physics.Bo Bian, Kazuhisa Sato, and Yoshihiko Hirotsu, "Ordering of island-like FePt crystallites with orientations", Appl. Phys. Lett. 75, 3686-3688 (1999) https://doi.org/10.1063/1.125429