We performed Fe-57 nuclear forward scattering experiments using a ferromagn
etic (Co0.94Fe0.06)(74.5)Si13.5B12 amorphous ribbon at BL09XU of SPring-8.
The observed NFS spectra of the amorphous ribbon show quantum beats that de
cay faster than the expected from the lifetime. This fast decay is due to t
he distribution of the hyperfine magnetic fields. Decay rate determined fro
m NFS in the amorphous is about 2.5 times shorter than that of isolated Fe-
57 nuclei. This value is similar to one expected from the apparent peak wid
th of the ordinary transmission Mossbauer spectra.