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Extremely dense glasses in the Bi Sr Ca Cu O system have been made by splat quenching. Single superconducting transitions at 110 K have been observed in crystallized samples from both resistivity and magnetization shielding experiments. Magnetization J c has been found to increase greatly at high field (H= 5T) as copper and calcium rich precipitates are introduced into the system.

H c1 vs T has been measured from the magnetization curves for H//ab. H c1 (T) near T c follows an empirical form but does not saturate at low temperatures.

The upper critical field is determined from the onset of diamagnetism in dc magnetization measurements. The slopes of the upper critical field are −1.9 T/K and −10.5 T/K corresponding to coherence lengths of 16 A and 3 A parallel and perpendicular to the CuO-planes. The angular dependence can be described with a 3D anisotropic Ginzburg-Landau theory with a critical field anisotropy of five.

AC magnetoresistance measurements were performed on a single crystal of YBa 2 Cu 3 O 7−δ in order to study the effect of dissipative flux flow motion due to Lorentz force. We find the shape of the superconducting resistive transition curve in field to vary with the Lorentz force but the zero resistance temperature to be independent of flux motion.

The magnetic phase diagram of La 2 CuO 4 is determined from dc magnetization measurements for the field parallel and perpendicular to the plane of the layers. No phase transition between weak ferromagnetism and paramagnetism is found.

Superconducting properties of RBa 2 Cu 3 O 7−x (R  Y, Gd and Nd) are studied as oxygen stoichiometries are varied. The region of x where samples are superconducting becomes narrower as the ionic radius of the R-ion increases. Samples most unstable to oxygen variation (i.e., Nd123) have the highest T c .