The thermoelectric power of dilute gold-iron alloys

Abstract

We have measured the thermoelectric power of a number of Au-Fe alloys, with Fe concentrations between similar 10 and 1900 ppm. Measurements were made between 0.4 and 30 K in fields up to 70 kOe. The alloys exhibited the familar `giant' thermopower in zero field, the peak value observed being - 15 μ V K-1 at about 10 K. Both the order of magnitude and the temperature dependence of the zero-field thermopower agree fairly well with Kondo's theory of spin-flip scattering. The thermopower of all but the most dilute alloys shows an initial increase in a magnetic field, which we believe is caused by Fe-Fe interactions. The thermopower then decreases due to `freezing-out' of spin-flip scattering and a simple pair-interaction model accounts for most of this observed behaviour. For the most concentrated alloy the decrease is not observed, even for the maximum field applied. For still higher fields (and lower concentrations) the thermopower decreases approximately as 1/H, as is suggested by a recent perturbation calculation.