Summation curves for flux pinning in superconductors
Flux pinning in irradiated superconductors having either dislocation-loop or void microstrutures is reexamined. The elementary interaction force f/sub p/ can be accurately computed for such defects if their size is known from transmission electron microscopy. Data exist for a range of defects for which f/sub p/ varies by over a factor of 10/sup 4/. If the data for voids and dislocation loops are plotted as Q, the volume pinning force per defect, versus f/sub p/ at a given reduced induction b, the sets of data for each defect species overlap to form a single summation curve. This curve is not correctly described by either of the two most widely used summation models, the direct summation or the statistical summation of Labusch. The empirical summation curve runs parallel to, but a factor approx. =4 below, the direct summation curve at high f/sub p/ but bends to decrease approximately as f/sup 2//sub p/ at low f/sub p/. Increasing b produces a shift in the summation curve, parallel to the direct summation Q=f/sub p/ line, by a factor which is proportional to (1-b)/sup 2/. This shift is the origin of the peak effect which appears at high b for low f/sub p/ defect microstructures. The failure of the statistical theory is thought to result from the presence of flux-line dislocations in the flux-line lattice which produce both a large decrease and a dispersion in the local threshold force necessary for pinning centers to be effective.
- Research Organization:
- Department of Materials Science and Engineering and the Materials Science Center, Cornell University, Ithaca, New York 14853
- OSTI ID:
- 5201602
- Journal Information:
- J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 49:2; ISSN JAPIA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360104* -- Metals & Alloys-- Physical Properties
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DISLOCATIONS
IRRADIATION
LINE DEFECTS
MAGNETIC FLUX
MICROSTRUCTURE
NIOBIUM ALLOYS
NIOBIUM BASE ALLOYS
NIOBIUM COMPOUNDS
NIOBIUM NITRIDES
NITRIDES
NITROGEN COMPOUNDS
PHYSICAL RADIATION EFFECTS
PNICTIDES
RADIATION EFFECTS
SUPERCONDUCTORS
TANTALUM ALLOYS
TRANSITION ELEMENT COMPOUNDS
TYPE-II SUPERCONDUCTORS
VOIDS