Effect of Strip Width on Low-Field Peak Effect of Critical Current Density in Bi_2Sr_2CaCu_2O_<8+δ> Superconducting Strips(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We investigate the dependence of the critical current density J_c along the crystal a-axis on the magnetic field along the c-axis at high temperatures below the superconducting transition temperature in individual Bi_2Sr_2CaCu_2O_<8+δ> (Bi-2212) whiskers with surface barriers by electrical transport measurements. J_c shows a low-field peak effect; J_c increases with the magnetic field in a low-field region and shows a peak at the threshold field H_<peak> below 100Oe. A comparison of the low-field peak effects in whiskers of different widths shows that H_<peak> depends on the sample width (i.e., the lateral dimension); the lateral axis is perpendicular to the magnetic field and the direction of current flow. A decrease in the sample width ω shifts H_<peak> toward a higher field. This systematic variation in H_<peak> with ω implies that the low-field peak effect observed in the Bi-2212 whiskers is associated with the effect of the finite ω on dilute vortices.
社団法人日本物理学会の論文
2009-02-15