Observation of a cubic defect in nickel by means of nuclear magnetic resonance on oriented¹¹⁴In nuclei

Abstract

114mIn was implanted at room temperature into nickel single crystals, and nuclear magnetic resonance was detected by observing the destruction of beta -asymmetry in the decay of 114In. After annealing at 400 K, at which temperature indium atoms are known to trap defects of vacancy-type, two single resonance lines were observed, corresponding to hyperfine fields of -3.30(1) T for the substitutional indium atoms, and +5.12(2) T for the defect associated indium atoms. The experiments were carried out with an external magnetic field along the (100), (110) and (111) crystallographic axis, respectively. No significant shift or splitting of the defect associated resonance line was detected. This implies that the defect causes an electric field gradient of at most 1017 V cm-2. It is argued that the defect is a cubic vacancy cluster as observed on the system (111In to 111Cd)Ni with perturbed angular correlations and Mossbauer spectroscopy on (119In to 119Sn)Ni.

Magnetism of isolated cadmium atoms in vacancy-associated sites in nickel

“…1 Similar frequencies had been found after different preparations, and especially the nature of the C-site defect has extensively been studied by nuclear techniques ranging from TDPAC, Mössbauer effect, 15 to NMR. 43 Using emission channeling measurements the existence of the tetrahedral interstice was confirmed. 44 The results of many investigations have been taken as support for the above allocations, but with the advent of the current measurements, experimentalists using the TDPAC technique have to pay sufficient attention to the peculiarities of the combined interaction before they can reduce the number of configurations they are discussing.…”

“…In Fig. 4, the theoret- ical results, which have originally been calculated for the n = 8 and n = 7 nickel surface sites, 31 are compared with the experimentally determined fields at vacancy-associated sites of Cd in nickel ͓this work͔, of In in nickel, 17,43 and with the values which are given for the other elements in de Waard's paper. 18 The expected fields which are estimated for other coordination numbers deviate significantly from the fields for the n = 8 and n = 7 clusters.…”

“…Preceding NMR measurements on In in nickel were insensitive to field gradients lower than V zz Ϸ 10 17 V / cm 2 . 43 Reliable estimates for magnetic hyperfine fields at the vacancy-associated Cd sites in nickel bulk are also necessary to be obtained. In accordance with the coordination-number dependence, which was originally found to work for spelements at surface sites, identical magnetic fields are assumed for configurations which are associated with equal numbers of vacancies.…”