Improved soft magnetic properties and thermal stability for Fe82·65Cu1·35Si2B14 alloys with Nb, Zr, Ta or Co addition

Abstract Nanocrystalline Fe81·65Cu1·35Si2B14M (M = Ta, Nb or Zr) alloys were obtained by melt spinning followed by annealing. The addition of Ta, Nb or Zr not only significantly increased the ΔTx of the Fe82·65Cu1·35Si2B14 alloy, which is defined as the temperature interval between the first and second crystallisation temperatures, but also had advantages in reducing grain size. In particular, Zr doping increased ΔTx from 91 to 155·2°C, and the Fe81·65Cu1·35Si2B14Zr alloy had good soft magnetic properties even after annealing at 500°C. Ta added alloy can still maintain fine grain size below 35 nm after annealing at 450°C. The effects of partial replacement of Fe with Co in the (Fe1−xCox)82·65Cu1·35Si2B14 alloys (x = 0, 0·3, 0·5 and 0·7) on the structure and magnetic properties were also investigated. Increasing the Co content reduced the first crystallisation temperature, and 30%Co substituted alloy had the highest saturation magnetisation. Co improved the thermal stability through increasing both Curie temperature Tc of the amorphous phase and ΔTx.