Sensitivity of the anomalous thermoelectric power to lattice defects in a dilute copper-iron alloy

Abstract

The thermoelectric power (TEP) of a Cu-Fe alloy containing 115 at ppm iron in the temperature range 1.5–80 K is measured in its unannealed state as well as after annealing at 530–550 C under fore-vacuum for 16 and 66 h, respectively. The TEP curves present a giant negative peak, which increases numerically with annealing and also shifts to lower temperatures. This observed numerical increase of the peak TEP value is attributed to the removal of the lattice defects rather than the decrease of the effective isolated impurity concentration consequent upon a partial precipitation of the impurity during annealing. Such an explanation is quite consistent with our inference of a phase shift for ordinary scattering increasing with impurity concentration in dilute magnetic alloys characterized by a negatives-d exchange interaction. The shift of the TEP peak to lower temperature is caused by an increase of the phonon drag component due to the removal of lattice defects. Such a decrease of the temperature of the peak TEP,Tp, is reminiscent of a similar variation of its counterpart,TK in electrical resistivity. However,Tp seems to be even more sensitive to the physical environment of the magnetic impurity.