2007 Volume 48 Issue 10 Pages 2612-2615
L10 nanocrystalline FePt alloy is directly formed by rapid quenching the melt with simultaneous addition of Zr and B and high coercivity can be obtained in the composition range of (Fe0.55Pt0.45)78Zr2–4B18–20. Single domain characteristic of the nanocrytalline FePt grains is clarified by Lorentz micorosocpy. Through the measurement of original magnetization curve and hysteresis loop, it is proposed that the mechanism of coercivity belongs to nucleation type. Distributions of lines of magnetic flux at demagnetized state and remanent state for two samples of (Fe0.55Pt0.45)78Zr4B18 and (Fe0.55Pt0.45)78Zr2B20 are observed by electron holography through ex situ experiment by applying a magnetic field. Obvious differences in the reconstructed phase images indicate the difference of the coercivities of the two samples.