The asymptotic region of the charge density oscillation around impurities in dilute copper-based alloys

Abstract

The wipe-out number for the first order quadrupole effect in the magnetic resonance of the matrix nuclei was measured in dilute copper-based alloys to study the asymptotic behaviour of the charge density oscillation around different impurities. The measured values are Cu-Zn: 490 ± 25; Cu-Au: 880 ± 40; Cu-Ni: 1250 ± 125; Cu-Pd: 1200 ± 100; Cu-Pt: 1900 ± 100. For the non-transition metal impurities the experimental values were compared with the predictions from Friedel's oscillation theory by using phase shifts calculated by the Blatt, Kohn-Vosko, Alfred-Van Ostenburg, Hurd-Gordon or the pseudo-atom method. For the transition metal impurities the phase shifts evaluated by Béal-Monod were used. On the assumption of resonance scattering for these impurities, the l = 2 phase shift was evaluated from the measured first order wipe-out number. This number was used also in combination with the impurity resistivity and the Friedel sum rule for calculating the phase shifts η 0, η 1, η 2 for the transition metals. The experimental values obtained in the asymptotic region give lower extrapolated charge density oscillation at the first and second neighbours of the impurity than that inferred by Rowland from the second order quadrupole effect and measured directly via satellite detection by Redfield and Schumacher et al.