The electrical and thermal conductivities of dilute copper-chromium alloys at low temperatures

Electrical and thermal conductivity measurements are reported on dilute copper-chromium alloys containing 32 and 50 at. ppm chromium, in their unannealed state and also after annealing at 530–550°C for 16 and 66 h in each case, under fore-vacuum. From the electrical resistivity measurements evidence of a possible cluster formation is obtained in the annealed sample. The electronic Lorenz number of the alloys increases with decrease of temperature in the temperature range 4.2–1.6 K. Lower temperature measurements might show a maximum around the Kondo temperature (～1 K) as predicted by the available theories on dilute magnetic alloys.