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Magnetically-Related Properties of Bismuth-Based High Tc Superconductors

Published online by Cambridge University Press:  28 February 2011

G.C. Vezzoli ,
M.F. Chen ,
F. Craver ,
T. Burke ,
B.M. Moon ,
A. Safari ,
B. Lalevic  and
W. Stanley
G.C. Vezzoli
Affiliation:
U. S. Army Materials Technology Laboratory, Watertown, MA
M.F. Chen
Affiliation:
U. S. Army Materials Technology Laboratory, Watertown, MA
F. Craver
Affiliation:
U. S. Army Materials Technology Laboratory, Watertown, MA
T. Burke
Affiliation:
U.S. Army Pulsed Power Laboratory, Ft. Monmouth, NJ
B.M. Moon
Affiliation:
Rutgers University, Busch Campus, Piscataway, NJ
A. Safari
Affiliation:
Rutgers University, Busch Campus, Piscataway, NJ
B. Lalevic
Affiliation:
Rutgers University, Busch Campus, Piscataway, NJ
W. Stanley
Affiliation:
Decisxon Software Company, Cambridge, MA
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Abstract

The effect of magnetic fields to 15T on the electrical resistance (R) of Bi-Sr-Ca-Cu-O superconductors has been measured at precise temperatures during the transition to the superconducting state. The results show that the temperature at which the externally-applied magnetic field causes a divergence of resistance (R) as a function of inverse temperature is approximately at the same temperature where the positive Hall coefficient begins its steep descent to zero. At slightly higher temperature the Hall coefficient shows a singularity peak akin to a delta function. Internal electric field calculations show that the structure of the superconducting oxides, having more than a single building block polyhedron, gives rise to strong electrostatic fields in the unit cell which in turn causes charge separation or polarization. The charge separation is in accord with the importance of high oxidation states of the multivalence cations and suggests the use of high oxygen overpressure during processing. The magnitude of Tc scales closely with the number of bound holes (associated with the charge transfer excitations) per unit cell. Extensive computer calculations using this model indicate attractive pairing of electrons at inter-electron separations of about 10–15A.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 169: Symposium M – High Temperature Superconductors: Fundamental Properties and Novel Materials Processing , 1989 , 1053
Copyright
Copyright © Materials Research Society 1990

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References

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