Evolution and the concomitant disappearance of high- Tc superconductivity with carrier concentration in the La sub 2 minus x Sr sub x CuO sub 4 minus. delta. system (0. 0 le x le 1. 2): Crossover from a Mott insulator to a band metal

Journal Article · Mon Jan 01 00:00:00 EST 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.41.371· OSTI ID:6910334

Sreedhar, K; Ganguly, P ^[1]

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1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (IN)

Electrical resistivity, magnetic susceptibility, thermogravimetric analysis, and infrared absorption spectra of the compound La{sub 2{minus}{ital x}}Sr{sub {ital x}}CuO{sub 4{minus}{delta}} have been studied for a wide range of Sr concentrations (0.0{le}{ital x}{le}1.2). The samples annealed at an oxygen pressure of 1 bar were stoichiometric ({delta}=0.0) in the range 0.0{lt}{ital x}{lt}0.33. In this range the compounds are characterized by a decrease in the {ital a} parameter, an increase in the {ital c} parameter, and a maximum in the {ital c}/{ital a} ratio (at {ital x}=0.33) typical of the formation of low-spin Cu{sup 3+} ions. In the range 0.15{lt}{ital x}{lt}0.33, the compounds show a positive temperature coefficient of resistivity, decrease in the magnitude of the Pauli magnetic susceptibility, infrared oscillator strengths, thermopower {ital S}, as well as the Hall coefficient {ital R}{sub {ital H}}. The superconducting transition temperature {ital T}{sub {ital c}} as well as the percentage Meissner fraction also decrease with {ital x} in this range. In particular the stoichiometric {ital x}=0.33 composition having a hole concentration of {similar to}0.33 holes/Cu shows a minimum in the Pauli magnetic susceptibility and disappearance of all infrared absorption bands. The superconductivity also disappears down to 4.2 K at this composition, even though it is more metallic. These results have been attributed to the occurrence of a transition from a highly correlated narrow-band Mott conductor'' to a broadband metal at high carrier concentrations. At still higher Sr concentrations (0.33{lt}{ital x}{lt}1.0), holes and oxygen vacancies coexist.

• OSTI ID: 6910334
• Journal Information: Physical Review, B: Condensed Matter; (USA), Vol. 41:1; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COPPER OXIDES
SUPERCONDUCTIVITY
LANTHANUM OXIDES
STRONTIUM OXIDES
ABSORPTION SPECTRA
CARRIER DENSITY
CHARGE CARRIERS
ELECTRIC CONDUCTIVITY
HOLES
INFRARED SPECTRA
MAGNETIC SUSCEPTIBILITY
ORDER-DISORDER TRANSFORMATIONS
PHASE TRANSFORMATIONS
QUANTITY RATIO
TRANSITION TEMPERATURE
VACANCIES
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELECTRICAL PROPERTIES
LANTHANUM COMPOUNDS
MAGNETIC PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POINT DEFECTS
RARE EARTH COMPOUNDS
SPECTRA
STRONTIUM COMPOUNDS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
656100 - Condensed Matter Physics- Superconductivity