Dedicated to Professor Dr. K. W. BOER on the occasion of his 70th birthday Measurements of dc and ac susceptibility, resistivity, Hall effect, and thermoelectric power (TEP) on pure phase Hg-1223 and mixed phase Hg-1212-1223 cuprates are reported. The mixed phase compounds show the highest critical temperature (magnetic susceptibility onset of 138 K). Both Hall effect arid TEP data support an underdoped state with hole-like conduction. Oxygen annealing reduces the Hall coefficient (increasing the concentration of holes) and lowers the TEI' (increasing the Fermi energy) features which can be explained by a simple Fermi-gas picture. The Hall coefficient which increases linearly with temperature and the negative temperature coefficient of the TEP, however, cannot be explained by single-hand Fermi-gas or -liquid theory, unless one introduces energy dependent carrier scattering. Estimates of the highest critical temperature based on the universality observed in the thermopower data for the cuprates suggest that 138 K is near the maximum one might expect for the Hg cuprates under optimal doping at atmospheric pressure.
Electronic and magnetic properties of the new 120 K Tl-Ca-Ba-Cu-O superconductor are presented. Resistance-temperature variations, ac susceptibility, and the (low) magnetic field dependence of the critical current density are reported. The new superconductor can be prepared in a molten state, which should allow processing leading to high critical current density. Preliminary x-ray diffraction data are also presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.