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

The ordered L10-FePt phase with a size of 20–200nm was directly formed by rapidly quenching the melt in the compositional range of 2–5at.% Zr and 17–20at.% B, and the alloys exhibit coercivity (Hc) higher than 200kA/m in an as-quenched state. In particular, the melt-spun (Fe0.50Pt0.50)78Zr4B18 alloy...

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Bibliographic Details
Published in:Journal of non-crystalline solids 2007-10, Vol.353 (32-40), p.3655-3660
Main Authors: Makino, Akihiro, Bitoh, Teruo, Nakagawa, Mai
Format: Article
Language:English
Subjects:
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Magnetic properties
Materials science
Nanocrystalline materials
Nanoparticles
Nanoscale materials and structures: fabrication and characterization
Phases and equilibria
Physics
Processing
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Summary:The ordered L10-FePt phase with a size of 20–200nm was directly formed by rapidly quenching the melt in the compositional range of 2–5at.% Zr and 17–20at.% B, and the alloys exhibit coercivity (Hc) higher than 200kA/m in an as-quenched state. In particular, the melt-spun (Fe0.50Pt0.50)78Zr4B18 alloy exhibits high Hc of 684kA/m. The melting temperature (Tm) remarkably decreases by the addition of Zr and B, e.g., from 1837K for FePt to 1345K 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 20–200nm 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 1345K of (Fe0.50Pt0.50)78Zr4B18 to 1083K of (Co0.50Pt0.50)78Zr4B18. However, Hc drastically decreases from 684kA/m of (Fe0.50Pt0.50)78Zr4B18 to 12kA/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.
ISSN:0022-3093
1873-4812
DOI:10.1016/j.jnoncrysol.2007.05.129