Effect of flux re-distribution on resistivity in granular YBCO

Authors: MUHAMMAD MUNEEB ASIM, SYED KHURSHID HASANAIN

Abstract: Dc resistivity of a zero-field cooled YBCO was previously studied as a function of angle between applied field and transport current. The resistivity followed a sin^{2}\theta variation that was understood as a consequence of Lorentz force like effect. The resistivity deviated from the harmonic curve giving a minimum at low angles before following the true sin^{2}\theta behavior. The angle corresponding to minimum voltage \theta_{min} has been thoroughly studied in this paper as a function of applied field, transport current and temperature. sin^{2}\theta behavior of resistivity is not affected by the fields below Hc1 at their respective temperatures. The angle \theta_{min} reduces with increasing fields and vanishes at about fields of 8 kOe for 77K. \theta_{min} also decreases with increasing values of current and temperature when studied under constant externally applied field. The data are explained as a consequence of Lorentz force-mediated flux re-distribution in the inter- and intragranular regions which further support the idea of controversial Lorentz force-like dissipation. Key Word: Polycrystalline YBCO, dc resistivity, angular dependence, Lorentz force-like effect.

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