Structure and magnetic properties of melt-spun Fe–Pt–B alloys with high B concentrations

Abstract

The phase evolution, thermal stability, structure and magnetic properties of the melt-spun Fe70−xPtxB30 (x=0–20) alloys have been investigated. Addition of small amounts of Pt to the Fe70B30 alloy increases the amorphous-forming ability, leading to the formation of an amorphous phase in the alloys with x=5 and 10. Further increase in Pt content results in the formation of the fcc-FePt+Fe2B or fcc-FePt+L10-FePt+Fe2B crystalline phases. After appropriate annealing, the homogeneous nano-sized structure consisting of hard L10-FePt and soft Fe2B magnetic phases were formed for the alloys with x=10–20, which exhibited good hard magnetic properties. As the Pt content increase, the coercivity (iHc) of the L10-FePt/Fe2B nanocomposite alloys significantly increased, while the remanence (Br) decreased. The Br, reduced remanence (Mr/Ms), iHc, and energy product (BH)max of the alloys are in the range of 0.81–1.20T, 0.76–0.84, 173.2–523.1kA/m, and 64.0–88.3kJ/m3, respectively.