The low-field magnetoresistance of single crystals of dilute copper- and silver-based alloys

The low-field magnetoresistance of single crystals of some dilute copper-and silver-based alloys has been measured at 1.5 K and 4.2 K. The alloys studied were Cu Au and Ag Au (homovalent impurity): Cu Zn and Cu Ge (heterovalent impurity); and Cu Ni and Ag Pd (transition metal impurity). The results, in conjunction with previously measured Hall coefficients, were interpreted under the assumption that an anisotropic relaxation time can be defined which has a different anisotropy for each impurity. By describing the anisotropy in terms of `relaxation time models' a possible variation in the relaxation time over the Fermi surface has been deduced for the Cu Au, Ag Au, Cu Ni and Ag Pd alloys, but the magnetoresistance of the Cu Zn and Cu Ge alloys cannot be interpreted in terms of the models described here.