Satellite structure of59Co NMR spectra in some Co alloys

Co alloys with Cr, Fe, Ru and Cu in the low concentration range have been studied by 59 Co NMR. Regularly spaced satellite lines are observed that develop with increasing impurity concentration. The satellite intensities as a function of the impurity concentration have been compared with the binomial distribution law of particular Co environments. Deviations from the exact binomial law in some cases are briefly discussed against the properties of their respective phase diagrams. From this comparison it is concluded that satellite frequencies are primarily determined by the number of impurity atoms in the first neighbour shell: each additional impurity atom in the shell introduces a constant (element-dependent) modification to the hyperfine field value on a Co site. This assignment of satellite frequency shifts to given configurations in the first coordination shell provides references for structural investigations in related binary metallic systems such as metallic multilayers. Preliminary results for CoPt alloys are also presented which do not follow the systematics of the previous alloys but rather suggest an extended oscillating perturbation around Pt impurities.