Magnetic impurities in superconductors: A theory with different predictions

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

DOI:https://doi.org/10.1103/PhysRevB.49.15799· OSTI ID:7307223

Kim, Y; Overhauser, A W ^[1]

---

1. Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States)

The proclivity of paramagnetic solutes to degrade the transition temperature of a traditional singlet-pairing superconductor is studied anew. [ital T][sub [ital c]] degradation is proportional to the (conduction electron) spin-disorder scattering rate, 1/[tau][sub [ital s]], caused by the solute spins. Accordingly the [ital T][sub [ital c]] loss increases with solute concentration. The initial slope (versus 1/[tau][sub [ital s]]) is found to depend on the superconductor and therefore is not the universal constant proposed by Abrikosov and Gor'kov. Instead the decrease is inversely proportional to [lambda], the electron-phonon coupling constant. Consequently a weak superconductor is doubly jeopardized by paramagnetic impurities: Its superconductivity is easily suppressed not only because [ital T][sub [ital c]] is small to begin with, but also because the initial slope is steeper. Another unexpected consequence of the theory involves potential scattering which, acting alone, does not significantly influence [ital T][sub [ital c]] (as surmised by Anderson). Nevertheless, the [ital T][sub [ital c]] reduction caused by exchange scattering will be partially suppressed when the overall mean free path becomes smaller than the coherence length. This compensation has been demonstrated experimentally by comparing the influence of magnetic impurities in a pure host superconductor with that in a similar host having (also) nonmagnetic solutes. Such observed recovery of [ital T][sub [ital c]], expected from this study, contradicts prior theories for magnetic solutes.

• OSTI ID: 7307223
• 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
COUPLING
ELECTRON-PHONON COUPLING
MAGNETIC PROPERTIES
MAGNETISM
PARAMAGNETISM
PHYSICAL PROPERTIES
RELAXATION TIME
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE