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Journal Article
Temperature dependences of the surface resistance and the diamagnetic shielding susceptibility at T/sub c/-T/spl Lt/T/sub c/ for high-T/sub c/ superconductors
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- Authors
- Hyun-Tak Kim, Kwang-Yong Kang, Seok-Kil Han
- Issue Date
- 2001-03
- Citation
- IEEE Transactions on Applied Superconductivity, v.11, no.1, pp.3415-3418
- ISSN
- 1051-8223
- Publisher
- IEEE
- Language
- English
- Type
- Journal Article
- Abstract
- At Tc - T << Tc (i.e., near Tc), in order to demonstrate the conduction mechanism and temperature dependencies of the diamagnetic-shielding susceptibility and the penetration depth, we fabricated Ba1-xKxBiO 3 (BKBO) thin films and measured the energy gap by tunnel effect and shielding susceptibilities which are compared with those measured for BKBO and YBCO single crystals. The shielding susceptibilities for BKBO and YBCO crystals well-fit ??(T)/??(0) = 1 - exp(-2??(T)/kBT), while that for the BKBO film follows ??(T)/??(0) = (1 - T/Tc) which may not be intrinsic. The exponential decrease of the susceptibilities near Tc indicates that the conduction mechanism is hopping. The energy gaps are observed as 2??(0) = (3.5짹0.1)kBTc for the BKBO film by the tunnel effect, 2??(0) = (3.9짹0.1)kBTc for the BKBO single crystal, and 2??(0) = (8짹0.2)kBTc for the YBa2Cu3O7 single crystal. Furthermore, for microwave device applications of superconductors, at Tc - T < < Tc, the surface resistance Rs(T)≈?닖?됌?0/2/?긪+ (?긯(0)-?긪)f(T) is derived from the surface impedance at ?됍꼝r <<1, where ?긯(0) and ?긪 are the conductivities of the superconducting state and the normal state, respectively, and f(T) = ??(T)/??(0) = (1 - exp(-2??(T)/kBT)).
- KSP Keywords
- As 2, At t, Energy gap, Normal state, Single crystal, Superconducting state, Surface impedance, conduction mechanism, device applications, microwave devices, penetration depth