Magnetoresistance of untwinned YBa2Cu3Oy single crystals in a wide range of doping:: Anomalous hole-doping dependence of the coherence length -: art. no. 167005

Magnetoresistance (MR) in the a -axis resistivity of untwinned YBa2Cu O-3(y) single crystals is measured for a wide range of doping (y = 6.45-7.0). The y dependence of the in-plane coherence length xi(ab) estimated from the fluctuation magnetoconductance indicates that the superconductivity is anomalously weakened in the 60-K phase; this observation, together with the Hall coefficient and the a -axis thermopower data which suggest the hole doping to be 12% for y similar or equal to 6.65, gives evidence that the origin of the 60-K plateau is the 1/8 anomaly. At high temperatures, the normal-state MR data show signatures of the Zeeman effect on the pseudogap in underdoped samples.