Local atomic structure of Fe–Co–Ln–B(Ln=Sm,Tb or Dy) amorphous alloys with supercooled liquid region

The local ordering structures of Fe70Co10B20 and Fe67Co10Ln3B20(Ln=Sm,Tb or Dy) alloys have been studied by X-ray diffraction. The analyses of interference functions and radial distribution functions revealed that the local atomic ordering becomes weaker and the coordination number of transition metals around Fe decreases while that of transition metals around B remains almost unchanged by the addition of Ln element to Fe–Co–B alloy. These results indicate that the amorphous phase consists of (Fe,Co)–B-based rigid local structure units and the Ln atom is inserted between them. The unique structure may cause the appearance of supercooled liquid region with the difficulty of re-arrangement of atoms during annealing.