Amorphous to crystalline transformation of ultrafine Fe62B38 particles

doi:10.1016/0304-8853(89)90241-2

Journal of Magnetism and Magnetic Materials

Volume 81, Issues 1–2, September 1989, Pages 138-146

https://doi.org/10.1016/0304-8853(89)90241-2 Get rights and content

Abstract

Fe₆₂B₃₈ particles, with sizes of 10–200 nm, have been produced by chemical reduction of Fe(II) ions in aqueous solution by KBH₄. Electron and X-ray diffraction, X-ray absorption fine structure and Mössbauer spectroscopy results reveal that the particles are amorphous. The Mössbauer parameters and the estimates of temperatures for crystallization and for ferromagnetic to paramagnetic transition suggest that the amorphous structures are similar for the particles and ribbons or films produced by liquid-squench or sputtering. The increase of the magnetic hyperfine field with annealing temperature, as deduced from ⁵⁷Fe Mössbauer spectroscopy, is attributed to atomic rearrangement in the amorphous phase. Crystalline Fe₂B and α-Fe are the products when the particles are annealed in Ar and H₂ at around 715 K. It is proposed that iron and boron partly separate during the initial stages of crystallization and subsequently form Fe₂B. Passivation of the particles makes them oxidatively stable, even when heated in air at temperatures up to 650 K.

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Hence in our system the contribution with B4 = 22.9 T arises due to the embedding of four B atoms into the nearest coordination spheres of iron. The field B5 = 20.3 T is typical of Fe62B38 amorphous alloy [21], meanwhile in [3] similar contribution is ascribed to the insertion of five B atoms into the nearest surrounding of Fe atoms. The contribution with B6 = 17.5 T have not been reported for the Fe–B system so far.
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Amorphous to crystalline transformation of ultrafine Fe62B38 particles

Abstract

Mater. Sci. Eng.

J. Magn. Magn. Mat.

Solid State Commun.

Appl. Phys. Lett.

Appl. Phys. Lett.

Phys. Rev. Lett.

IEEE Trans. Magn. MAG-14

Nature

Amorphous to crystalline transformation of ultrafine Fe₆₂B₃₈ particles