Examination of the c-axis resistivity of Bi2Sr2−xLaxCuO6+δ in magnetic fields

We measure the magnetic-field dependence of the c-axis resistivity, ρc(H), in a series of Bi2Sr2−xLaxCuO6+δ (BSLCO) single crystals for a wide range of doping using pulsed magnetic fields up to 58 T. The behavior of ρc(H) is examined in light of the recent determination of the upper critical field Hc2 for this material using Nernst effect measurements. We find that the peak in ρc(H) shows up at a field Hp that is much lower than Hc2 and there is no discernable feature in ρc(H) at Hc2. Intriguingly, Hp shows a doping dependence similar to that of Tc, and there is an approximate relation kBTc ' 12gμBHp. Moreover, we show that the data for the lowest-Tc sample can be used to estimate the pseudogap closing field Hpg, but the method to estimate Hpg proposed by Shibauchi et al. [Phys. Rev. Lett. 86, 5763 (2001)] must be modified to apply to the BSLCO system.