Magnetic Field Depreciation of the Kondo Resistivity forCu1−XAuX−FeandCu1−XAuX−CrSystems

Abstract

For ${\mathrm{Cu}}_{1\ensuremath{-}X}{\mathrm{Au}}_{X}\ensuremath{-}\mathrm{Fe}$ alloys near Cu-Fe, the component of the magnetoresistance due to depreciation of the Kondo state by field has been determined. The presence of the gold constituent suppresses the normal magnetoresistance to negligible values. For ${\mathrm{Cu}}_{1\ensuremath{-}X}{\mathrm{Au}}_{X}\ensuremath{-}\mathrm{Cr}$ alloys near Cu-Cr, the technique is only partially successful due to difficulties in dissolving Cr in ${\mathrm{Cu}}_{1\ensuremath{-}X}{\mathrm{Au}}_{X}$ when $X$ is appreciable. At zero field, the resistivity of Cu-Fe and similar systems with a few atomic percent Au depends strongly on the heat treatment of the specimens. Apparently, lattice distortion or defects increase the $d$-wave phase shift for normal potential scattering. The experimental results suggest a renormalization of the Hamann solution for the spin-scattering part of the $t$ matrix similar to the Schotte transform. For ${\mathrm{Cu}}_{99.5}$${\mathrm{Au}}_{0.5}$-Fe and ${\mathrm{Cu}}_{95}$${\mathrm{Au}}_{5}$-Fe, the initial field dependence of the negative Kondo contribution to the magnetoresistance is ${H}^{2}$ as suggested by the anomalous-Green's-function theory by Kurata. A much slower dependence on $H$ is found as the field approaches 100 kG.