Initial magnetization and coupling nature of the high- T sub c grains in Bi-Pb-Sr-Ca-Cu-O

Journal Article · Wed May 01 00:00:00 EDT 1991 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.43.10455· OSTI ID:5561684

Oota, A; Noji, H ^[1]; Ohba, K ^[2]

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1. Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Tempaku-cho, Toyohashi, Aichi 441, Japan (JP)
2. Technical Research and Development Laboratories, Topy Industries Ltd., Akemi-cho, Toyohashi, Aichi 441, Japan (JP)

The coupling between grains was studied through low-field ({lt}100 Oe) initial magnetization {ital M}({ital H}) on bulk samples of Bi-Pb-Sr-Ca-Cu-O with a single high-{ital T}{sub {ital c}} (110 K) phase prepared under different sintering times {ital t}{sub {ital s}}. The {ital M}({ital H}) shows a variation with changing {ital t}{sub {ital s}} due to the weak links between grains and its behavior is characterized by three threshold fields: {ital H}{sub 1}{sup {ital B}}, {ital H}{sub 2}{sup {ital B}}, and {ital H}{sub 3}{sup {ital B}}. The first flux entry into the sample along the grain boundaries due to flux creep occurs at {ital H}{sub 1}{sup {ital B}}, much lower than {ital H}{sub {ital c}1}{sup {perpendicular}} ({similar to}7 Oe at 77 K, {similar to}15 Oe at 0 K) for {bold H}{perpendicular} {ital c} axis determined from the {ital c}-axis-oriented tape with {ital J}{sub {ital c}}=5400 A/cm{sup 2} (77 K, {ital H}=0). Between {ital H}{sub 1}{sup {ital B}} and {ital H}{sub 2}{sup {ital B}}, {ital M}({ital H}) deviates from a straight line due to shielding of the sample volume; between {ital H}{sub 2}{sup {ital B}} and {ital H}{sub 3}{sup {ital B}} it falls on the Meissner line, an effect ascribed to electrically decoupled grains. The first flux entry into the grains themselves occurs at {ital H}{sub 3}{sup {ital B}}, above which {ital M}({ital H}) is governed by the intragrain magnetic properties of an Abrikosov lattice. Prolonged sintering improves the weak links between the grains and suppresses both the flux creep at the grain boundaries and the electrical decoupling between grains, which opens transport current paths and leads to the rise in {ital T}{sub {ital c}}({rho}=0).

• OSTI ID: 5561684
• Journal Information: Physical Review, B: Condensed Matter; (USA), Vol. 43:13; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BISMUTH OXIDES
MAGNETIZATION
CALCIUM OXIDES
COPPER OXIDES
LEAD OXIDES
STRONTIUM OXIDES
GRAIN BOUNDARIES
HIGH-TC SUPERCONDUCTORS
MAGNETIC FLUX
ALKALINE EARTH METAL COMPOUNDS
BISMUTH COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTAL STRUCTURE
LEAD COMPOUNDS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
STRONTIUM COMPOUNDS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties