Investigation of magnetic properties, phase evolution, and microstructure of Fe56.7Pt25.3M2B16 (M = Ta, Nb, Ti, and Zr) melt-spun ribbons

Effects of refractory elements on the phase evolution, magnetic properties, and microstructure of melt-spun Fe56.7Pt27.3B16 and Fe56.7Pt25.3M2B16 (M = Ta, Nb, Ti, and Zr) ribbons have been investigated. It is found that multiple phases, namely magnetically hard L10-FePt, magnetically soft Fe2B and Fe3B phases, can be readily formed in the above alloy ribbons after an isothermal annealing treatment. The refractory elements on the Fe56.7Pt25.3M2B16 ribbons tend to react with boron to form borides or a solid solution along the grain boundaries, which impedes the disorder to order transformation of L10-FePt phase. A higher annealing temperature is necessary for the formation of ordered L10-FePt phase, giving rise to the formation of coarse grains or inhomogeneous grains. Consequently, the intrinsic coercivity (iHc) and reduced remanence ratio (σr/σ12 kOe) are reduced from 7.5 kOe and 0.85 for Fe56.7Pt27.3B16 to 3.3–6.1 kOe and 0.75–0.81 for Fe56.7Pt25.3M2B16, respectively.