Amorphous (Fe40Ni40B19Cu1)10o-xNbx (x =1,3,5,7) ribbons are prepared by using the melt-spinning method.We find that the glass forming ability (GFA) of the as-melt spun ribbons is significantly improved by adding Nb element.In addition,the thermal stability evaluated in steps of △T =Tx2-Tx1 effectively increases from 16 K to 75 K with Nb content increasing.The as-melt spun (Fe40Ni40Bi9Cu1)97Nb3 ribbon exhibits a lowest coercivity of 2 A/m and relatively large saturation magnetization of 103.7 A·m2/kg and thus it can be further treated by being annealed at 809 K.The crystallization behavior is confirmed to be determined by two individual crystallization processes corresponding to the precipitation of (Fe,Ni)23B6 phase and γ-(Fe,Ni) phase.With increasing annealing time,the single (Fe,Ni)23B6 phase can be transformed into a mixture of (Fe,Ni)23B6 and γ-(Fe,Ni) phase,and the grain size of γ-(Fe,Ni) phase increases from 5 nm to 80 nm while the grain size of (Fe,Ni)23B6 remains almost unchanged.Finally,we find that the grain growth in each of (Fe,Ni)23B6 and γ-(Fe,Ni) deteriorates the overall magnetic properties.