THE ELECTRONIC SPECIFIC-HEAT OF YBA2 (CU1-XZNX)3O7 FROM 1.6-K TO 300-K

Using a differential technique we have determined between 1.6 K and 300 K and for 0≤x≤0.1 the difference in electronic specific heat coefficients γ(x, T)- γ(0.07, T)n of YBa2(Cu1-xZnx)3O7 and a YBa2(Cu0.93Zn0.07) reference. The results are consistent with a superconducting Fermi liquid and cannot be readily described in terms of the condensation at Tc of bosons preformed above Tc. We deduce γ(x, T) from these results, and find γn = 1.6±0.2 mJ/(g-at.K2) (density of states N (EF) = 8.8 states/(eV.fu)) independent of x. Superconducting anomalies are seen for all samples, with Tc and the anomaly height decreasing and γ(x, 0) increasing with x consistent with magnetic pair breaking. The thermodynamic critical field Hc(x, T) is determined for 0≤x≤0.07. We observe a (nearly) universal temperature dependence for the low temperature magnetic anomalies in Zn-doped and undoped samples with broad specific heat maxima at or above 5 K. For undoped YBa2Cu3O7 we find θ(0) = 406 K and an electronic term γ(0, 0) = 0.15±0.15 mJ/(g-at. K2) substantially smaller than the generally quoted value. © 1990.