Magnetic and thermal properties of high Tc super conductors

Measurements of the normal state magnetic susceptibility chi(T) of YBa2Cu3O7, Bi(1.8)Pb(0.2)Sr2CaCu2O(8 + delta), and Bi(2-x)Pb(x)Sr2Ca2Cu3O(10 + delta) (x = 0.2 and 0.25) were carried out. All chi(T) data show negative curvature below approximately 2 (Tc). The data for YBa2Cu3O7 are in excellent agreement with a new calculation of the superconducting fluctuation diamagnetism. From the analysis, an s-wave pairing is inferred and microscopic parameters are obtained. For chi(T) of YBa2Cu3O7, part of the negative curvature is inferred to arise from the normal state background. A strong temperature dependent anisotropy delta(chi) is equivalent to chi(sub c) - chi(sub ab) was found and the normal state spin contributions were estimated to chi(T). The heat capacity C(T) of YBa2Cu3O7 is reported for 0.4 K is less T is less than 400 K in zero and 70 kG magnetic fields. In addition to the feature associated with the onset of the superconductivity at (Tc), two anomalies in C(T) were observed near 74 and 330 K, with another possible anomaly near 102 K; the temperatures at which they occur correlate with anomalies in chi(T) and ultransonic measurements. The occurrence of the anomaly at approximately or equal to 330 K is found to be sample-dependent. The influences of a magnetic field and the thermal and/or magnetic field treatment history dependence of a pellet sample on C(T), the entropy and the influence of superconducting fluctuations on C(T) near (Tc), and the possible source of the observed intrinsic nonzero gamma(0) at low T are discussed.