on d - m at / 0 10 73 52 v 1 [ co nd - m at . s up r - co n ] 1 7 Ju l 2 00 1 Thermopower and thermal conductivity of superconducting perovskite
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چکیده
The thermopower and thermal conductivity of superconducting perovskite M gCN i 3 (T c ≈ 8 K) have been studied. The thermopower is negative from room temperature to 10 K. Combining with the negative Hall coefficient reported previously, it definetly indicates that the carrier in M gCN i 3 is electron-type. There is a small phonon-drag-like thermopower peak around 35 K. Above 56 K the nonlinear temperature dependent thermopower can be fitted with the modified mixed-valency formula (mixed-valency and the diffusion contribution). The thermal conductivity is of the order for intermetallics, larger than that of borocarbides and smaller than M gB 2. A small but clear decrease of thermal conductivity is observed at T c = 8 K. In the normal state the electronic contribution to the total thermal conductivity is slightly larger than the lattice contribution. The transverse magnetoresistance of M gCN i 3 is also measured. It is found that the magnetoresistance is small and positive, following the classical Kohler's rule over a wide temperature range.
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