Low-Temperature Transport Properties of Dilute Silver-Manganese Alloys

We report measurements of the electrical resistivity between 20 and 0.3 K and the thermal conductivity between 4 and 0.6 K of a number of dilute alloys of manganese dissolved in silver. The nominal concentration range of the alloys is from 0.005- to 1.1-at.% Mn. The electrical-resistivity curves for the more concentrated alloys show a resistance maximum at an anti-ferromagnetic ordering temperature $T_{max}$ which is a characteristic for this alloy system. At lower temperatures, however, a resistivity that is approximately a linear function of temperature is observed. The Lorenz number for the alloys turns out to be concentration dependent, although the deviations from $L_0$, the Sommerfeld value for the Lorenz number, are generally not more than about 4%. The results are interpreted in terms of a phenomenological model based on the classical Kondo theory, together with a Lorentzian distribution of internal magnetic fields that exist at an impurity site.