OUT-OF-PLANE MAGNETORESISTANCE OF BI2SR2CACU2O-DELTA-CRYSTALS - PROBING THE FLUCTUATION-INDUCED PSEUDOGAP IN THE DENSITY-OF-STATES(X SINGLE)

We report on measurements of the out-of-plane resistivity and magnetor esistance in the normal state region above the critical temperature T- c in optimally doped and overdoped Bi2Sr2CaCu2O8+x single crystals. Th e temperature dependence of the out-of-plane resistivity indicates the rmally activated hopping of carriers over an interplane pseudogap. In the overdoped samples this behavior gradually changes to a metallic-li ke resistivity at higher temperatures. The out-of-plane magnetoresista nce (measured with the magnetic field parallel to the current) is nega tive, indicating a shrinking of the pseudogap in magnetic fields. Our experimental results are in good accordance with a recent model for th e reduction of the quasiparticle density of states due to condensation of quasiparticles into superconducting fluctuations. Such a fluctuati on-induced pseudogap is expected to be suppressed in high magnetic fie lds according to a reduction of the in-plane fluctuation amplitude.