Antiferromagnetic correlations and the normal-state transport in heavily underdoped YBa 2Cu 3O 6+ x

The Néel ordering in heavily underdoped YBa ₂Cu ₃O _{6+ x} has remarkably different impact on the electron transport within CuO ₂ planes and between them. While the in-plane resistivity and magnetoresistance (MR) are smooth through the Néel temperature T_N, the out-of-plane transport demonstrate striking anomalies, e.g. the MR increases by two orders of magnitude at T_N. These observations give evidence that the spin fluctuations play the key role in the out-of-plane transport and that the charge confinement within the CuO ₂ planes is related to the spin degrees of freedom. We discuss whether the picture of charged stripes can account for these features.