We present the resistively determined upper critical field Hρc2(T) and the irreversibility lines Hρirr(T) of various high-Tc cuprates, deduced from measurements in 61-T pulsed magnetic fields applied parallel to the c axis. The shape of both Hρc2(T) and Hρirr(T) depends monotonically on the anisotropy of the material and none of the samples show saturation of Hρ(T) at low temperatures. The anomalous positive curvature d2Hρ/dT2 > 0 is the strongest in materials with the largest normal state anisotropy, regardless of whether anisotropy is varied by changing the carrier concentration or by comparing a variety of optimally doped compounds.
|Number of pages
|Physical Review B - Condensed Matter and Materials Physics
|Published - 1999