2002 Volume 43 Issue 8 Pages 2125-2129
Using a time differential perturbed angular correlation (TDPAC) method with 111In which decays to 111Cd, the lattice defects induced by cold rolling in Ni metal at 77 K have been studied by the magnetic hyperfine fields observed at the 111Cd probe nuclear sites. To investigate the dependence of annealing temperature, we have measured TDPAC spectra at 298 K during 1 hour isochronal annealing up to 1273 K in Ar+7%H2 gas atmosphere. After 1273 K annealing, only one component which shows ωL=98.0±0.5 Mrad/s corresponding to magnetic hyperfine field of 6.68±0.02 T has been observed at 300 K . This frequency is interpreted as a hyperfine field at 111Cd nucleus which occupies substitutionally the Ni lattice sites. We have also investigated the interaction between probe nucleus and lattice defects from the measurements of 111Cd TDPAC spectra. After deformation, distinctive changes have not been observed. But after 473 K annealing, ωL=40.60±1.03 Mrad/s corresponding to magnetic hyperfine field of 2.77±0.07 T was observed in addition to the component originating from the substitutional 111Cd atoms. This frequency seems to be due to the component from the trivacancy trapping site. Because 111In−V3 site might transform immediately to 111In−V4 complex, and shows the cubic environment. This component disappeared after annealing above 873 K, and after 1273 K annealing the spectrum completely returned to the original substitutional 111Cd spectrum before the cold rolling.
