Local structure in amorphous Fe-TM-Zr (TM = Co, Ni, Cu) studied by Mossbauer spectroscopy

Room temperature Mossbauer spectroscopy was used to investigate the link be tween local structure and crystallisation in amorphous (a) FexTM1-xZr2(TM = Co, Ni, Cu) (0 < x less than or equal to 1) alloys. As expected for a syst em that maintains a constant atomic structure, independent of the Fe-TM rat io, the isomer shift (delta) changed linearly with the TM content. The rate of increase with TM in the order Co < Ni < Cu is consistent with delta of isolated Fe impurities in these metals. For the cases of Co and Ni TMs, the quadrupole splitting (Delta) increased linearly as the iron content was re duced, the rate of change increasing as the atomic number increased, i.e., Co < Ni. This trend was also observed for the Cu series, however there was a change in slope for x < 0.3. As no reduction in the width of the quadrupo le splitting distribution was observed (sigma(Delta) approximate to 0.27 mm /s remained constant), the reduced growth in Delta is not due to the presen ce of improved ordering in local structural units. The change in Delta at x approximate to 0.3 can be directly attributed to the change in the mode of crystallisation indicating a change in the evolution of packing with compo sition in the amorphous phase. (C) 1999 Elsevier Science B.V. All rights re served.