Development of YBaCuO bulk superconductor for use as low magnetic field sensor

Polycrystalline samples of nonoriented bulk YBaCuO superconducting specimens display high degree of disorder, semiconducting behavior in the normal state, and broad transition temperature. A regime explaining electrical and magnetic behaviors of high critical temperature superconductors called thermally activated flux flow (TAFF) presents a state in which vortex dynamic exhibits an ohmic behavior. The resistivity in this regime is proportional to the applied magnetic field for small current densities. In this work is presented a systematic study of the magnetoresistance as a function of the applied magnetic field in the range 5 to 100 Oe for polycrystalline samples with various thickness. Results of X-ray diffraction, resistivity as a function of the temperature, I-V characteristic curves and magnetoresistance are shown. The later result was fitted through an ad-hoe model showing good agreement in the 5 to 100 Oe magnetic field range.