The Deviation from Matthiessen's Rule at 4.2 K in Dilute Copper-Gold-Germanium Alloys

Abstract

The deviation from Matthiessen's rule (DMR) of dilute copper-gold-germanium alloys was measured at 4.2, 77 and 273 K. The low-field Hall coefficient of binary Cu-Au and Cu-Ge alloys was also measured at 4.2 K to determine anisotropy parameters for the explanation of the DMR in the ternary alloys. In order to control the shape factor of the ternary samples the germanium content was brought into binary Cu-Au samples by vapour deposition and diffusion annealing. The limitation of the usual two-group model for the investigated alloys is shown and a more accurate three-group model is presented. Especially the DMR at 4.2 K of the ternary samples in the range 20-30 nΩ cm (as well as the DMR at 273 K) can be substantiated by the low-field Hall coefficient and by the anisotropy of scattering rates obtained from the de Haas-van Alphen effect for the binary alloys.