Variation of [ital T][sub [ital c]] and resistivity in charge-compensated (Ca[sub [ital x]]La[sub 1[minus][ital x]])(Ba[sub 1. 75[minus][ital x]]La[sub 0. 25+[ital x]])Cu[sub 3]O[sub [ital y]]

Journal Article · Wed Jun 01 04:00:00 EDT 1994 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.49.15928· OSTI ID:7307194

Goldschmidt, D; Knizhnik, A; Direktovitch, Y; Reisner, G M; Eckstein, Y ^[1]

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1. Department of Physics and Crown Center for Superconductivity, Technion Israel Institute of Technology, Haifa 32000 (Israel)

We report careful measurements of the transition temperature [ital T][sub [ital c]] of (Ca[sub [ital x]]La[sub 1[minus][ital x]]) (Ba[sub 1.75[minus][ital x]]La[sub 0.25+[ital x]])Cu[sub 3]O[sub [ital y]] as a function of oxygen content [ital y], mainly for compositions [ital x]=0.1 and 0.4. This 1:2:3 superconductor family, that exists in the composition range 0[le][ital x][le][similar to]0.5, is tetragonal and has a maximal [ital T][sub [ital c]] of [similar to]82 K. Through mutual charge-compensating cosubstitutions, it preserves a constant charge on the noncopper cations ([ital Q]=7.25), independent of [ital x]. We observed a monotonic decrease in [ital T][sub [ital c]] as [ital y] varies from the initial value [similar to]7.15 to the insulator state roughly at [ital y][congruent]6.9. At the metal-insulator (MI) transition, the value of [ital y][sub MI] decreases with increasing [ital x]. Most unusual is the substantial increase in [ital T][sub [ital c]] by 21 to 24 K when [ital x] changes from 0.1 to 0.4, under conditions where the charge density remains constant. It is accompanied by a twofold decrease in resistivity [rho]. We attribute this to the change in band structure with composition [ital x], which occurs due to increase in Ca content and to oxygen redistribution near La that substitutes for Ba. This induces a net electron transfer from the planes to the disordered chains. This assumption is supported by the decrease in [ital y][sub MI] and in lattice parameters with increasing [ital x]. It implies that changes in mobile hole density, which are responsible for the increase in [ital T][sub [ital c]] and decrease in [rho], take place despite the total charge density being constant.

• OSTI ID: 7307194
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 49:22; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

665411* -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
CHARGE DENSITY
COPPER COMPOUNDS
COPPER OXIDES
DOPED MATERIALS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRON TRANSFER
ELEMENTS
HIGH-TC SUPERCONDUCTORS
HOLE MOBILITY
MATERIALS
MOBILITY
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE