Paramagnetic moments and time effects in melt-textured NdBaCuO system with Nd422 inclusions


Paramagnetic moments and time effects in melt-textured NdBaCuO system with Nd422 inclusions

Dias, F. T.; Vieira, V. N.; Silva, D. L.; Wolff-Fabris, F.; Kampert, E.; Almeida, M. L.; Mesquita, F.; Hneda, M.; Roa, J. J.

We have performed magnetic measurements in two melt-textured NdBa2Cu3O7-╬┤ samples with Nd422 inclusions under magnetic fields from 0.05 up to 14 T, applied parallel to the ab planes. The measurements were made with a superconducting quantum interference device (SQUID) and a vibrating sample magnetometer (VSM). Paramagnetic moments could be observed during FCC (field-cooled cooling) and FCW (field-cooled warming) experiments. This effect, known as Paramagnetic Meissner Effect (PME), persisted up to 14 T and strong irreversibilities were observed among FCC and FCW experiments, revealing the presence of time effects. These time effects were confirmed by specific magnetic relaxation experiments in different cooling rates and temperatures, showing an anomalous and curious paramagnetic behavior. We explain our results based on the flux-compressed state generated within nonsuperconducting regions of the sample, such as the Nd422 inclusions dispersed into the superconducting matrix. These inclusions may produce a strong vortex pinning that stabilize the paramagnetic state, allowing the admission of extra vortices into the sample responsible for the positive moments during the relaxation experiments.

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Publ.-Id: 22156