Variation of vortex-glass dynamics and critical region with oxygen content in Bi 2Sr 2CaCu 2O 8+ δ single crystal

Abstract

A systematic analysis of disorder and anisotropy effects has been performed on the transport data of three oxygen doped Bi 2Sr 2CaCu 2O 8+ δ (BSCCO-2212) single crystals obtained in external magnetic field aligned with the crystal c-axis, ranging from 100 Oe to 40 kOe. The result confirms the existence of finite critical region in all cases and ostensible crossover behavior associated with 3-D vortex-glass transition. The maximum widths of the regions ([ T *− T g]/ T g=0.66, 0.53 and 0.38) as well as the critical exponents ( s=5.3±1.3, 3.8±0.7 and 2.8±0.6) are shown to decrease consistently with lower anisotropy ( γ 2=19,500, 8300 and 3000) corresponding to samples with increasing doping. While being responsible for the suppression of first-order melting, the effect of stronger disorder also contributes to larger temperature and field ranges of the critical region.