Electromagnetic Properties of Melt-Grown YBaCuO Superconductors Doped by Gd and Sm

M. Jirsaa, M. Rameša, D. Volochováb, M. Radušovskáb, P. Dikob aInstitute of Physics, ASCR, Na Slovance 2, CZ-182 21 Praha 8, Czech Republic bInstitute of Experimental Physics SAS, Watsonova 47, 040 01 Košice, Slovakia

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Electromagnetic properties of YBa2Cu3Oy samples melt-grown in air and doped with small amounts of light rare earth (LRE) ions Gd and Sm were studied. The LRE doping creates a point-like disorder contributing to the second peak on the magnetization curve. In the field range of the second peak the average magnetic moment, Mav, deduced from the magnetization curves exhibited strong fluctuations. Mav is commonly regarded as an equilibrium moment close to the thermodynamic reversible one, obeying in intermediate fields a logarithmic field dependence. However, in our experiments Mav(B) curves failed to follow such a dependence below irreversibility line. Mav(B) curves deduced from rather static measurements, done by SQUID magnetometer still showed the disturbance but significantly weaker. It indicates that this feature reflects the vortex dynamics in the second peak region. Its scaling with temperature was found to coincide with that of the pinning force.

DOI: 10.12693/APhysPolA.126.326 PACS numbers: 74.25.Ha, 74.25.Op, 74.25.Sv, 74.60.Ge, 74.72.-h