Structure and Magnetic Properties of Nanocompsite Fe-Pt-B Ternary Alloys

Abstract

The structures and magnetic properties of nanocompsite Fe-Pt-B ternary alloys were investigated in a wide composition range. A single amorphous phase was formed in the composition range of 0-15 at. % Pt and 20-30 at. % B, while the composition ranges of fcc-FePt + amorphous, fcc-FePt + Fe2B and L10-FePt + Fe2B/FeB phases were formed out the range of single amorphous. With more than 5 at. % of Pt, the crystallized structure consisting of nanoscale L10-FePt and Fe2B/FeB phases was obtained after annealing except for alloys with 0-10 at. % Pt and 15-25 at. % B. The annealed alloys with no less than 10 at. % of Pt exhibit good hard magnetic properties. Increasing Pt and B were propitious to increase the coercivity (iHc) of the alloys because of the enlargement of volume fraction for L10-FePt phase. The maximum values of iHc can reach 806.7 kA/m for Fe50Pt25B25 alloy after annealing at 843 K for 900 s. However, higher Pt content exceeding 20 at. % leads to the decrease of the iHc for alloys with more than 30 at. % B, which is due to the precipitation of FeB phase.

Keywords: Nanocompsite magnets, Melt-spinning, amorphous, L10-FePt phase, Coercivity