Pressure Effect on the Magnetic Properties of Superconducting Pb–Tl and Pb–In Alloys

Abstract

The pressure dependence of the Ginzburg-Landau parameter, κ, in some second-kind superconductors was measured. Pressures up to 3,000 atm were applied using a high pressure bomb with kerosene-oil mixture as the transmitting medium.
For Pb-3.5 at.% Tl and Pb-3.5 at.% In, dlnκ⁄dp is −12.6±1.8 and −12.1±4.5×10⁻⁶ atm⁻¹, respectively. The Gor’kov formula, which connects κ with the electronic specific heat coefficient, γ, and the residual resistivity, ρ, is well satisfied with the observed values of dlnκ⁄dp, dlnγ⁄dp and dlnρ⁄dp.
The difference in the pressure effect on the effective electron-electron interaction parameter between the above two alloys was found to be greater than that on γ, which is proportional to the density of states at the Fermi level.
The pressure dependence of the upper-critical field is in good agreement with the data calculated from the bulk modulus jump.