Low-temperature specific heat of YBa2Cu3O7, YBa2Cu3O6, Y2BaCuO5, YBa3Cu2O7, BaCuO2, and CuO |
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Authors: | D Eckert A Junod A Bezinge T Graf J Muller |
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Affiliation: | (1) Département de Physique de la Matière Condensée, Université de Genève, CH-1211 Geneva 4, Switzerland |
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Abstract: | We have measured the low-temperature specific heat (1.3 T 20 K) and the dc magnetic susceptibility (100 T 250 K) of eight samples of the high-T
c
superconductor Y
x
Ba3–x
Cu3O7– (x=0.9, 1.0, 1.1) and of two samples of nonsuperconducting YBa2Cu3O6+ . We have also performed specific heat measurements on the possible impurity phases: YBa3Cu2O7, Y2BaCuO5, CuO, and BaCuO2+x
. The superconducting samples all have a nonzero, sample-dependent linear term * and an upturn inC/T at very low temperature. We show that this anomalous behavior is at least partly due to the presence of a small amount ( 1%) of BaCuO2+x
impurity phase in the measured samples. This is evidenced by the correlation between * and the Curie component of the susceptibility, which is proportional to the amount of paramagnetic impurities. |
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Keywords: | |
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