Magnetic properties of the Bi1.95Sr2.05−xLaxCuOy (Bi-2201) superconducting phase |
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Authors: | G Triscone M S Chae M C de Andrade M B Maple |
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Institution: | Department of Physics and Institute for Pure and Applied Physical Sciences, University of California, San Diego, La Jolla, CA 92093, USA |
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Abstract: | We have investigated the reversible mixed-state magnetization M of three lanthanum substituted Bi1.95Sr2.05−xLaxCuOy (Bi-2201) ceramic samples having different critical temperatures Tc ranging from 20.0 to 35.5 K. As for the Bi2Sr2CaCu2O8+δ (Bi-2212) phase, we found that anisotropy of Bi-2201 is large. A manifestation of this anisotropy is the field independent magnetization M* observed at a temperature T*. In the framework of the London model, and including thermal fluctuations of vortices, we found for the temperature dependence of the penetration depth λab(T) = λab(0)1 − (T/Tc0)n]−1/2, with n 1.7 and λab (T = 0) 4000 Å. The estimated upper critical fields μ0Hc2,c are of the order of 10 T. We observe a peculiar negative slope M/T at low temperature and sufficiently high external magnetic field. This feature seems to be a characteristic of the Bi-2201 phase. However, we do not know whether it is associated with the superconducting mixed-state. A small amount of magnetic impurities could also be responsible for this behavior. Finally, the behavior of the reversible magnetization of the Bi-2201 samples investigated, which are situated at the optimal and in the overdoped region, did not indicate any unusual temperature dependence for the upper critical field Hc2,c. |
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Keywords: | Bi-2201 Magnetization Mixed-state Fluctuation Penetration depth Upper critical field |
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