Upper critical magnetic field of the heavy-electron superconductors U sub 1 minus x Th sub x Be sub 13 ( x =0 and 2. 9%) doped with paramagnetic Gd and other rare-earth ions

Journal Article · Tue Jan 01 04:00:00 EST 1991 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.43.299· OSTI ID:6115461

Dalichaouch, Y; Lee, B W; Lambert, S E; Maple, M B ^[1]; Smith, J L; Fisk, Z ^[2]

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1. Department of Physics and Institute for Pure and Applied Physical Sciences, University of California, San Diego, La Jolla, California 92093 (US)
2. Los Alamos National Laboratory, Los Alamos, New Mexico (USA)

The temperature {ital T} dependence of the upper critical magnetic field {ital H}{sub {ital c}2} of the heavy-electron superconductors U{sub 1{minus}{ital x}}Th{sub {ital x}}Be{sub 13} ({ital x}=0 and 2.9%) doped with various concentrations of Gd has been determined from low-frequency ac magnetic susceptibility measurements in magnetic fields up to 60 kOe. The {ital H}{sub {ital c}2}({ital T}) curves for U{sub 1{minus}{ital x}}Gd{sub {ital x}}Be{sub 13} samples deviate from the {ital H}{sub {ital c}2}({ital T}) curves of UBe{sub 13} near {ital T}{sub {ital c}}, which is consistant with the depairing of superconducting electrons via the Zeeman interaction between the spins of the superconducting electrons and the exchange field associated with the Gd spins. This suggests that UBe{sub 13} exhibits singlet superconductivity. In contrast, the {ital H}{sub {ital c}2}({ital T}) curves for (U{sub 0.97}Th{sub 0.03})Be{sub 13} doped with Gd scale with {ital H}{sub {ital c}2}({ital T}) of pure (U{sub 0.97}Th{sub 0.03})Be{sub 13} and do not reflect superconducting depairing by the Gd ions. These results are consistent with either strong spin-orbit scattering due to the presence of Th in UBe{sub 13}, or to a qualitatively different type of superconductivity involving triplet spin pairing in (U{sub 0.97}Th{sub 0.03})Be{sub 13}. Measurements of the temperature dependence of {ital H}{sub {ital c}2} for U{sub 1{minus}{ital x}R{ital x}}Be{sub 13} compounds where {ital R}=La, Lu, and Ce for various compositions {ital x} as well as U{sub 0.985}{ital R0.015}Be{sub 13} compounds for {ital R}=Tb, Dy, Ho, and Er are also presented and compared with the Gd-doped UBe{sub 13} system. The results of low-temperature specific-heat measurements of UBe{sub 13} doped with various concentrations of Gd are also discussed.

• DOE Contract Number: FG03-86ER45230
• OSTI ID: 6115461
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 43:1; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
ACTINIDE ALLOYS
ALLOYS
BERYLLIUM ALLOYS
BERYLLIUM BASE ALLOYS
CRITICAL FIELD
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
GADOLINIUM ADDITIONS
GADOLINIUM ALLOYS
MAGNETIC FIELDS
PHYSICAL PROPERTIES
RARE EARTH ADDITIONS
RARE EARTH ALLOYS
SPECIFIC HEAT
SUPERCONDUCTIVITY
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
THORIUM ALLOYS
ULTRALOW TEMPERATURE
URANIUM ALLOYS
ZEEMAN EFFECT