paper

In-plane anisotropy on the transport properties in the modulated Bi_2O_2-based conductors Bi-2212 and Bi-Sr-Co-O

arXiv:cond-mat/0204187 · doi:10.1016/S0921-4534(02)01407-7

Abstract

We investigated the in-plane anisotropy on the resistivity and thermopower of the Bi_2Sr_2CaCu_2O_{8+δ} (Bi-2212) and Bi-Sr-Co-O (BiCo) single crystals. In Bi-2212, the b-axis resistivity is higher than the a-axis resistivity, and is expressed as a sum of the a-axis resistivity and an additional residual resistivity. A downward deviation due to pseudogap is observed below a characteristic temperature T^*, which is isotropic in the form of conductivity. These results suggest that the modulation structure along the b-axis works as an anisotropic scattering center, but does not affect the pseudogap formation. On the other hand, the anisotropy of the resistivity and the thermopower in Pb-doped BiCo is substantial, probably owing to the misfit structure between the hexagonal CoO_2 layer and the rock salt Bi_2O_2 layer. However, the anisotropy in the resistivity in Pb-free BiCo is very small, suggesting that the in-plane anisotropy is averaged by the modulation structure, whose direction is tilted by 45 deg from the a- and b-axes.

arXiv comment4pages 5 figures, Proceedings of ISS2001, Physica C (in press)

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