We report on a comparative study of thermoelectric power measurements (S(T)) in ferrimagnetic Gd4(Co1-xAx)3 compounds with A = Cu, Pt, in the temperature range 8 K – 300 K. Whereas in Gd4Co3S(T) is always negative, for x > 0 the substitution of Co for Cu/Pt gives rise to the appearance of a low temperature positive maximum in S(T) at around 30 K. Based on our previous study of Gd4(Co1-xCux)3 compounds, we argue that this maximum in S(T) originates from electron-magnon scattering and is sensitive to electron band structure changes resulting from the substitution of Co for Cu/Pt and the accompanying reduction in the ratio between the electron-magnon and the electron-phonon scattering strengths. The decreasing role of Co 3d electrons with the progressive substitution of Co for Cu/Pt, evidenced by a strong reduction in the spin disorder resistivity and the Co magnetic moment, is seen to be crucial for the existence of such low temperature maximum in S(T) for x > 0. It is seen that the substitution of Co for Pt leads to higher values of the amplitude and temperature of the positive maximum in S(T) than the substitution of Co for Cu.
Linear mean free path and quadratic temperature dependence of electron-phonon scattering rate in V82Al18-xFex alloys at low temperature
