Upper critical fields in liquid-quenched metastable superconductors
A systematic and quantitative study of upper critical fields in alloys with increasing atomic number is carried out. The alloys are prepared by the technique of liquid (splat) quenching. They include the metastable body-centered-cubic (..beta..) phase of Ti-Pd, Zr-Mo, Zr-Pd, and Hf-Mo, amorphous phase of Zr-Rh, and the stable ..beta.. phase of Ti-Mo and Ta-Hf. Measurements are made in magnetic fields up to 90 kG and in temperatures down to 0.5 K. The results are analyzed within the framework of the dirty-limit theory of Werthamer, Helfand, Hohenberg, and Maki (WHHM). A least-squares fitting routine is performed using all the data (weighted equally) for a given sample. It is emphasized that the visual critical-field gradient near the transition temperature cannot be taken as the actual gradient in the presence of Pauli paramagnetic limitation. The main findings are the following: (i) Even without including renormalization corrections due to electron-phonon and electron-electron interactions, very good fits to the WHHM theory are obtained; (ii) critical-field data for all our samples (with minor exceptions in Hf-Mo)= are found to fall below or on the Maki curve (i.e., when the spin-orbit scattering parameter lambda/sub s.o./ goes to infinity); (iii) values of lambda/sub s.o./ are observed to range from 0.28 to 2.51 for the 3d and 4d alloys; (iv) the spin-orbit scattering rates 1/tau/sub s.o./ are found to compare well with theoretical estimation using results from band-structure calculation. The effect of sample inhomogeneity on the value of lambda/sub s.o./ in Zr-Mo alloys is also illustrated.
- Research Organization:
- Department of Physics, University of Virginia, Charlottesville, Virginia 22901
- OSTI ID:
- 6468546
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 30:3; ISSN PRBMD
- Country of Publication:
- United States
- Language:
- English
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOY SYSTEMS
ALLOYS
BINARY ALLOY SYSTEMS
CRITICAL FIELD
DATA ANALYSIS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
ENERGY LEVELS
EXCITED STATES
GINZBURG-LANDAU THEORY
MAGNETIC FIELDS
METALS
METASTABLE STATES
MOLYBDENUM ALLOYS
PALLADIUM ALLOYS
PHYSICAL PROPERTIES
PLATINUM METAL ALLOYS
SUPERCONDUCTIVITY
SUPERCONDUCTORS
TITANIUM ALLOYS
TRANSITION ELEMENTS
ULTRALOW TEMPERATURE
ZIRCONIUM ALLOYS