In La1.9-itxGd0.1SrxCuO4, a prominent change of the thermoelectric power S below ∼80K is observed in a narrow region of x around 0.12 although the structural phase transition to the tetragonal low-temperature (TLT) phase is observed at ∼ 115K in a wide region of x. These results suggest that the anomalous behaviors of the transport properties below ∼80K are responsible for the change of the electronic state itself. In La1.875-yGdySr0.125CuO4, Tuittdβ, which is the structural phase transition temperature to the TLT pahse, increases with increasing y. The temperature where S begins to decrease rapidly is close to Tudβ in y≤0.04. In y≥0.05, a prominent change of S is observed below a lower temperature than Tudβ and an obvious sign reversal of S appears appears at ∼40K. These results indicate that the change of the electronic state is enhanced in the TLT phase.
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