Shielding current density in Mg-doped YBCO-123 as determined by a.c. magnetic-susceptibility measurements
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High-resolution a.c. magnetic-susceptibility measurements have been performed on sintered samples of Mg-doped YBCO superconductors YBa2(Cu1−x Mg x )3O7−δ (δ≤0.08, 0≤x≤0.1). An estimation of the intergranular shielding currents J s (T, H d.c.) has been obtained by separating the grains and coupling-junctions contributions to the measured susceptibility. The results show that Mg doping increases the weak links weight and reduces the values of J s. At H d.c.=0, J s (T, 0) follows a power law of the type (1−T/T c)β, with β varying from 2 (undoped sample) to about 5 (x=2.5%). The dependence of J s on the applied d.c. magnetic field can be fitted to a Lorentzian lineshape whose width appears to be independent of the substitution level.
PACS74.70 Superconducting materials
PACS74.30 General properties
PACS74.60.Jg Critical currents
PACS74.60.Mj Material effects on Tc, x, critical currents (including impurities, ion implantation etc.)
PACS01.30.Cc Conference proceedings
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