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Reversible magnetization as a function of the oxygen concentration in Bi-2212 superconducting ceramics

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Published in Physica C: Superconductivity and Its Applications. 1995, vol. 242, no. 1-2, p. 143-154
Abstract We investigate the reversible magnetization in the mixed state of a batch of Bi2.12Sr1.90Ca1.02Cu1.96O8 + δ (Bi-2212) ceramics with different oxygen concentrations δ and superconducting transition temperatures Tc between 50 and 92 K. Additional data for a single crystal (Tc = 85 K) demonstrate the validity of the effective-mass model with essentially infinite anisotropy. The magnetization curves M(T) for different fields cross in a single point {M*(δ); T*(δ)} for all Tc's≥ 65K. The saturation magnetization M*(δ) is found to be proportional to T*(δ). This agrees with existing theories if the superconducting volume fraction, presumably 100%, does not vary with δ. The systematic suppression of the Meissner effect that is observed with decreasing Tc is therefore attributed to enhanced pinning. For Tc = 50 K, there is no single crossing point. This is attributed to a crossover to 3D in the strongly overdoped state. The penetration depth λ(T) is evaluated from limT→0 ∂M/∂lnH. The systematic dependence of λ(0) versus δ indicates that the carrier density increases with oxygen content, as expected.
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GENOUD, Jean-Yves et al. Reversible magnetization as a function of the oxygen concentration in Bi-2212 superconducting ceramics. In: Physica C: Superconductivity and Its Applications, 1995, vol. 242, n° 1-2, p. 143-154. https://archive-ouverte.unige.ch/unige:93802

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