Abstract
Abstract The specific heat of four samples of the 81 K-superconductor Yba 2 Cu 4 O 8 prepared under high oxygen pressure is investigated. The low-temperature specific heat is sample-dependent. For the most homogeneous sample, the coefficient of the linear term at T ⪡ T c is γ ∗ =4.9±0.2mJ/(K 2 mole) and the initial Debye temperature is θ (0)=350±10K. A small specific heat jump Δ C / T c =12 to 16 mJ/(K 2 mole) is observed at the superconducting transition; it is only weakly correlated with the field cooling Meissner fraction (14 to 55% in 20 Oe). A tentative separation of the total specific heat into electron and phonon terms is obtained by a least-squares fit of high-temperature data using a model of the phonon density of states. The electron contribution is found to be much smaller than for YBa 2 CU 3 O 7 . Thermochemical data are tabulated.
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