Field dependence of the superconductive penetration depth in tin up to the superheating limit
The superconductive penetration depth δ(T, H) has been studied as a function of temperature and field in single tin spheres, 15--30 μm in diameter. A mutual-inductance method was used with the 75-kHz measuring field parallel to the static field. When properly normalized, the variation of the transition signal with T and H is then proportional to dδ-bar (T, H) times H/dH, where delta-bar is the penetration depth averaged over the sphere surface. The results are independent of sphere diameter, and thus characteristic of bulk tin. In zero field δ (T) = δ0/1 - (T/Tc)41/2, with δ0 = 520 plus-or-minus 30 A. The field dependence was studied for temperatures close to Tc and fields up to the ideal bulk superheating field Hsh approx. = 2.76Hc, corresponding to a Ginzburg-Landau parameter kappa = 0.093 ± 0.001. The penetration depth increases sharply as the field approaches Hsh, but stays finite, while its derivative diverges. We find δ(Hsh)/δ (H = 0) = 1.51 ± 0.04. Averaged over the sphere, we have delta-bar (Hsh)/δ-bar (H = 0) = 1.19 ± 0.01. The field dependence is rather well described by one-dimensional Ginzburg- Landau theory in the low-kappa limit. The results indicate that the surface order parameter psis is depressed by 30 to 50 % at Hsh . In ''weak'' fields, H less than or equal to 1.5Hc, the data are consistent with the customary quadratic field dependence.
- Research Organization:
- Institute of Physics, University of Oslo, Oslo 3, Norway
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-33-017772
- OSTI ID:
- 4117247
- Journal Information:
- Physical Review, B: Solid State, Vol. 12, Issue 11; Other Information: Orig. Receipt Date: 30-JUN-76; ISSN 0556-2805
- Country of Publication:
- United States
- Language:
- English
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