Direct synthesis of L10-(Fe, Co)Pt nanocrystallites from (Fe, Co)-Pt-Zr-B liquid phase by melt-spinning

Akihiro Makino, Teruo Bitoh, Mai Nakagawa

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The ordered L10-FePt phase with a size of 20-200 nm was directly formed by rapidly quenching the melt in the compositional range of 2-5 at.% Zr and 17-20 at.% B, and the alloys exhibit coercivity (Hc) higher than 200 kA/m in an as-quenched state. In particular, the melt-spun (Fe0.50Pt0.50)78Zr4B18 alloy exhibits high Hc of 684 kA/m. The melting temperature (Tm) remarkably decreases by the addition of Zr and B, e.g., from 1837 K for FePt to 1345 K for (Fe0.55Pt0.45)78Zr4B18. The L10 phase with Zr and B directly formed by the rapidly quenching shows high thermal stability and maintains up to Tm. The simultaneous addition of Zr and B facilitates the direct formation of the ordered L10 phase with a grain size of 20-200 nm by rapidly quenching the melt through the effect of the decreasing Tm and the increasing the stability of the L10 phase by the solution of Zr and B into the phase. The substitution of Fe by Co monotonously decreases Tm from 1345 K of (Fe0.50Pt0.50)78Zr4B18 to 1083 K of (Co0.50Pt0.50)78Zr4B18. However, Hc drastically decreases from 684 kA/m of (Fe0.50Pt0.50)78Zr4B18 to 12 kA/m of (Co0.50Pt0.50)78Zr4B18, which has a single fcc structure in an as-quenched state. The decrease in Hc with increasing Co content up to Fe:Co = 1:3 is caused by the decreasing of the magnetocrystalline anisotropy, which originates from the decreasing the long-range order parameter of the L10 phase.

Original languageEnglish
Pages (from-to)3655-3660
Number of pages6
JournalJournal of Non-Crystalline Solids
Volume353
Issue number32-40
DOIs
Publication statusPublished - 2007 Oct 15
Externally publishedYes

Keywords

  • Magnetic properties
  • Nanoparticles
  • Phases and equilibria
  • Processing

ASJC Scopus subject areas

  • Ceramics and Composites
  • Electronic, Optical and Magnetic Materials

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