Mössbauer study of Nd5Fe77-xCrxB 18 (x = 0, 3 and 5) nanocomposite magnets

K. Suzuki, J. M. Cadogan, K. Aoki

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Abstract

The magnetic properties of amorphous Nd5Fe77-xCr xB18 (x = 0, 3 and 5) after annealing at 953 K for 0.6 ks have been investigated by means of 57Fe Mössbauer spectroscopy with particular attention paid to the effect of heating rate on the proportions of the magnetically hard and soft phases. The hard Nd2Fe 14B phase is absent from Nd5Fe77B18 regardless of heating rate. On the contrary, ∼10 mol% of Nd 2Fe14B is confirmed for Nd5Fe 7.2Cr5B18 and the molar fraction of Nd 2Fe14B is almost independent of heating rate. Hence, the intrinsic coercivity of Nd5Fe77B18 is as low as ∼ 10kA/m while that of Nd5Fe72Cr5B 18 shows a high value > 300 kA/m. On the other hand, the proportion of the hard and soft phases for Nd5Fe74Cr 3B18 is highly dependent on the heating rate and the fraction of Nd2Fe14B increases from 0 to 12 mol% with increasing heating rate from 0.042 to 1.33 K/s. This microstructural change results in a dramatic enhancement of the coercivity from 9 to 370 kA/m.

Original languageEnglish
Pages (from-to)1481-1483
Number of pages3
JournalJournal of Magnetism and Magnetic Materials
Volume226-230
Issue numberPART II
DOIs
Publication statusPublished - 1 Jan 2001
Externally publishedYes

Keywords

  • Coercivity
  • Crystallization kinetics
  • Flash annealing
  • Hyperfine fields

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