Abstract
From the temperature dependence of the specific heat of the semiconductor La2CuO4 and the high temperature superconductors La1.8Sr0.2CuO4 (T c =37.2 K) and YBa1.9K0.1Cu3O6.9 (T c =91.5 K) in the range 1.5–30 K, a strong similarity of the lowfrequency part of their phonon density of states with a peak around 10 meV could be inferred. In the case of La1.8Sr0.2CuO4 the thermodynamical critical field belowT c has been determined and using the Rutger's formula and the BCS model, a Sommerfeld coefficient γ=9 mJ·mol−1 K−1 was obtained, which, taking into account recent results of band structure calculations leads to an electron-phonon enhancement factor γ=1.3, value compatible withT c =36 K when using McMillan's formula forT c . A systematic study of the magnetization offered evidence for strong flux trapping effects at higher fields and for Meissner shielding by superconducting Josephson currents in fields below 6 mT at 4.2 K.
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Rosenberg, M., Mittag, M., Job, R. et al. A specific heat and magnetization study of highT c ceramic superconductors. Z. Physik B - Condensed Matter 69, 151–157 (1987). https://doi.org/10.1007/BF01307270
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DOI: https://doi.org/10.1007/BF01307270