Superconducting phase transitions in rare-earth compounds

Journal Article · Wed Nov 01 04:00:00 EST 1978 · Phys. Rev., B: Solid State; (United States)

DOI:https://doi.org/10.1103/PhysRevB.18.4688· OSTI ID:6462897

Maekawa, S; Tachiki, M

The superconducting transition temperrature T/sub c/ and the upper critical field H/sub c/2 in the rare-earth (R) compounds R/sub x/Mo/sub 6/S/sub 8/, R/sub x/Mo/sub 6/S/sub 8/, R/sub x/Mo/sub 6/Se/sub 8/, and RRh/sub 4/B/sub 4/, are theoretically studied within a model in which the superelectrons mainly originate from the 4d electrons of Mo and Rh atoms. The fluctuation of local spins inside a Cooper pair weakens the BCS coupling. Thus, the quantities T/sub c/ and H/sub c/2 are strongly influenced by the fluctuation. These quantities are obtained as functions of the intra- and interatomic exchange interactions and the concentration of the spins. The theoretical results explain the existence of the upperr and lower superconducting transition temperatures T/sub c/1 and T/sub c/2 in ErRh/sub 4/B/sub 4/ and Ho/sub 1.2/Mo/sub 6/S/sub 8/, and the concentration dependence of T/sub c/ in La/sub 1-x/Gd/sub x/Mo/sub 6/Se/sub 8/ and Sn/sub( 1.21-x/)Eu/sub x/Mo/sub 6.35/S/sub 8/. The suppression of the spin fluctuation by application of a magnetic field causes an increase of the BCS coupling. In calculating H/sub c/2, this fact is taken into account as well as the spin splitting of conduction bands and spin-orbit scattering. Our theory explains the anomalous behavior of the temperature dependence Our theory explains the anomalous behavior of the temperature dependence of H/sub c/2 observed in Sn/sub( 1.21-x/)Eu/sub x/Mo/sub 6.35/S/sub 8/. It is proposed that in certain compounds a superconducting state may appear only in the presence of a magnetic field.

• Research Organization: The Research Institute for Iron, Steel, and Other Metals, Tohoku University, Sendai, 980 Japan
• OSTI ID: 6462897
• Journal Information: Phys. Rev., B: Solid State; (United States), Journal Name: Phys. Rev., B: Solid State; (United States) Vol. 18:9; ISSN PLRBA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
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& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BCS THEORY
BORIDES
BORON COMPOUNDS
CHALCOGENIDES
CRITICAL FIELD
ERBIUM BORIDES
ERBIUM COMPOUNDS
EUROPIUM COMPOUNDS
EUROPIUM SULFIDES
GADOLINIUM COMPOUNDS
GADOLINIUM SELENIDES
HOLMIUM COMPOUNDS
HOLMIUM SULFIDES
LANTHANUM COMPOUNDS
LANTHANUM SELENIDES
MAGNETIC FIELDS
MOLYBDENUM COMPOUNDS
MOLYBDENUM SELENIDES
MOLYBDENUM SULFIDES
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
RHODIUM BORIDES
RHODIUM COMPOUNDS
SELENIDES
SELENIUM COMPOUNDS
SULFIDES
SULFUR COMPOUNDS
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TIN COMPOUNDS
TIN SULFIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
TYPE-II SUPERCONDUCTORS