Luzuriaga, J., A. Badía-Majós, G. Nieva, J. L. Giordano, C. Lopez, A. Serquis, and G. Serrano. "Magnetic relaxation induced by transverse flux shaking in MgB2 superconductors." Superconductor Science and Technology 22 (2009): 15021.
Abstract: We report on measurements and numerical simulations of the behavior of MgB2 superconductors when magnetic field components are applied along mutually perpendicular directions. By closely matching the geometry in simulations and measurements, full quantitative agreement is found. The critical state theory and a single phenomenological law, i.e. the field dependence of the critical current density Jc(B), are sufficient for a full quantitative description of the measurements. These were performed in thick strips of carbon nanotube doped MgB2 samples. Magnetization was measured in two orthogonal directions using a SQUID magnetometer. Magnetic relaxation effects induced by the application of an oscillatory perpendicular field were observed and simulated numerically. The measurements confirm the numerical predictions, that two relaxation regimes appear, depending on the amplitude of the applied magnetic field. The overall agreement constitutes a convincing validation of the critical state model and the numerical procedures used.
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Luzuriaga, J., A. Badía-Majós, G. Nieva, J. L. Giordano, C. Lopez, A. Serquis, and G. Serrano. "Experimental and numerical study of transverse flux shaking in MgB2 superconductors." In Journal of Physics: Conference Series, 012009. Vol. 167., 2009.
Abstract: Magnetization measurements in the mixed state of thick strips of carbon nanotube
doped MgB
2
in crossed fields configurations are reported, together with numerical simulations
performed with a geometry equivalent to the sample shape. The samples were subjected to
magnetic field components along mutually perpendicular directions, an oscillatory field in one
direction and a remanent magnetization in the perpendicular direction. The magnetic response
along the oscillatory field and the magnetic relaxation perpendicular to it are observed and
simulated using the critical state theory. A remarkable quantitative agreement between the
experiment and the theory was obtained.
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Giordano, J. L., J. Luzuriaga, Ruíz-Tagle, G. NIEVA, and Badía-Majós. "Magnetization measurements of hard superconductors under dissipative transport." Journal of Physics: Conference Series 43, no. 1 (2006): 663–666.
Abstract: The hysteretic magnetic flux dynamics of ceramic type-II superconductors under superimposed transport current cycles has been investigated. Field cooled and zero field cooled experiments were carried-out on polycrystalline YBa 2Cu3O7-x cylinders by using both temperature and applied field control, to drive the sample into the semi-reversible granular regime. The transport current magnitude was near and above the dissipative threshold. The interplay between shielding and transport due to vortex-pinning interactions, equilibrium magnetization effects, and diamagnetic/paramagnetic relaxation phenomena are shown to play an important role in the range of practical applications.
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Conte, V., J. L. Giordano, J. J. Zarate, and J. Luzuriaga. "Superconducting Devices for Radioastronomy; First Steps in Chile: SNS-junction Fabrication.", 424–427. Vol. 1., 2010.
Abstract: We present results of the microfabrication of Josephson Junctions (JJs) of Superconductor-Normal-superconductor (SNS) type, as a first step in the acquisition of the know-how of superconducting devices applied to radioastronomy. A twojunction SQUID was built using a Nb/Al bilayer deposited on a Si wafer. The procedure needs only one mask and a single UV exposure (i.e., one photolithography step). We show the micrograph and the observed non linear characteristic I-V curve at 4K of the first device fabricated in the framework of ALMA Grant 31090010.
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Giordano, J. L., J. Luzuriaga, A. Badía-Majós, G. Nieva, and I. A. Ruiz-Tagle. "Magnetization collapse in polycrystalline YBCO under transport current cycles." Superconducting Science and Technology 19, no. 4 (2006): 385–391.
Abstract: We report measurements of the hysteretic magnetization of YBCO under superimposed transport current cycles, together with numerical simulations of magnetization and current density profiles in the corresponding parallel configuration. Field cooled (FC) and zero-field-cooled (ZFC) experiments were carried out on polycrystalline YBa2Cu3O7?x cylinders, with both the applied magnetic field and transport current in the axial direction, and the current cycled several times, around and above the dissipative threshold. As in previously reported multicomponent field configuration experiments, the magnetization is seen to collapse to a more stable state both in FC and ZFC, because of the interplay between the shielding and transport currents. The results of our numerical simulations are in good qualitative agreement with the measurements, and the competition between shielding and transport due to vortex-pinning interactions and equilibrium magnetization effects are shown to play an important role in the range of our experiments.
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