Thermoelectric power of Gd4(Co1-xCux)3 compounds

Abstract

We report results of thermoelectric power measurements (S(T)) in ferrimagnetic Gd 4 (Co 1-x Cu x ) 3 compounds with x ¼ 0.05, 0.1, 0.2, and 0.3, in the temperature range 8-300 K. Whereas in Gd 4 Co 3, S(T) is always negative, for x > 0 the substitution of Co for Cu gives rise to the appearance of a low temperature positive maximum in S(T) at around 30 K. Based on our previous study of these 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 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, 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 a low temperature maximum in S(T) for x > 0.

Thermoelectric Power of Gd₄(Co-A)₃ Compounds (A = Cu, Pt)

“…1. In these compounds, the S(T) curves exhibit a set of features that were also reported for the Cu substituent compounds [9] and which can be summarized as follows.…”

“…In this work, we investigated the sensitivity of thermoelectric power to the normal metal (Cu/Pt) substituent of Co by comparing previously reported results of S(T) in Gd 4 (Co 1-x Cu x ) 3 compounds [9] with here reported results of S(T) for Gd 4 (Co 1-x Pt x ) 3 compounds.…”

“…The effects on the thermoelectric power of such band structure changes were also investigated [9]. It has been found that, whereas in Gd 4 Co 3 S(T) is always negative, for x > 0 the substitution of Co for Cu gives rise to the appearance of a low temperature positive maximum in S(T) at around 30 K. It was argued 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 and the accompanying reduction in the ratio between the electron-magnon and the electron-phonon scattering strengths.…”

Comments on the thermoelectric power of the f-electron metallic compounds

“…1,2 The fundamental researches are focused both on the SCES, see e.g. Refs [3][4][5][6][7][8][9][10][11] as well as on the well-localized f-electron systems (WLS) -see Refs [12][13][14][15][16][17][18][19]. The thermoelectric power (TEP) of the SCES reaches typically the values one or two orders greater than those of the WLS, but in both material groups it exhibits the anomalies as the sign change and/or the maxima (minima).…”

“…In some experimental works (see e.g. Refs [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]) one can find the interpretations of TEP anomalies as caused by the isotropic s-f exchange scattering (in the one-band approach for the conduction electrons) and/or the electron-phonon scattering -considered in the Born approximation. These interpretations are based on the results of Refs [34][35][36] where the TEP maxima and the sign reversal were obtained within these oversimplified models.…”