Phase Transition in the Vortex Structure of Granular YBa2Cu3O7-delta HTSCs in Weak Magnetic Fields

作者：Sukhareva T V^*; Finkel V A

来源：Journal of Experimental and Theoretical Physics, 2008, 107(5): 787-793.

DOI：10.1134/S1063776108110083

This study aims at establishing the interrelation between the current-carrying capacity and peculiarities of magnetoresistance of granular YBa2Cu3O7-delta HTSCs (T-c = 92.5 K). The transverse magnetoresistance of several batches of YBa2Cu3O7-delta HTSC samples with noticeably different values of critical supercurrent density j(c) is measured in magnetic fields H-ext up to H-ext(max) approximate to 500 Oe in a wide range of transport currents (5 mA <= I <= 1600 mA) at T = 77.4 K. Samples with relatively high values of j(c) (H-ext = 0) >= 100 A/cm(2) do not exhibit any anomalies in their field dependences. Magnetoresistance jumps delta rho(BG-VG)/rho(273K) are observed for samples with low values of j(c) <= 20 A/cm(2) in fields HBG-VG approximate to 200 - 260 Oe. The width Delta HBG-VG of the anomalous resistance region increases upon an increase in I. The magnetoresistance jumps decrease with increasing I in increasing field H-ext(0 -> H-ext(max)) and increase in decreasing field H-ext (H-ext(max) -> 0). It is found that these peculiarities of the field dependences of magnetoresistance are associated with a first-order phase transition (in magnetic field) in the vortex structure of YBa2Cu3O7-d HTSCs of the Bragg glass-vortex glass type.

• 出版日期2008-11