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

The phase evolution, thermal stability, structure and magnetic properties of the melt-spun Fe_70-xPt_xB₃₀ (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 (_iH_c) of the L1₀-FePt/Fe₂B nanocomposite alloys significantly increased, while the remanence (B_r) decreased. The B_r, reduced remanence (M_r/M_s), _iH_c, and energy product (BH)_max of the alloys are in the range of 0.81-1.20 T, 0.76-0.84, 173.2-523.1 kA/m, and 64.0-88.3 kJ/m³, respectively.