The freezing of spin and charge at low temperature in YBa2Cu3O6+x

We present the results of an extensive μSR reinvestigation of the doping dependence of the AF order in polycrystalline YBa2Cu3O6+x samples (0<x<0.4), prepared by a topotactic-like technique which yields oxygen equilibrated and ordered pairs of YBCO samples of well defined oxygen order conditions. For x>0.2, we detected a spin freezing correlated to the charge freezing of the holes in the CuO2 planes. The data may be fitted to a model of size-dependent reduction of the staggered magnetization implied in a stripe scenario. The hole concentration dependence of these freezing phenomena is mapped onto the phase diagram of YBa2Cu3O6+x.