PHASE-SEPARATION IN ANTIFERROMAGNETIC YBA2CU3O6+X

We present a detailed study of the ZF-mu SR precession signals in AF Y Ba2Cu3O6+x for a series of 0.06 less than or equal to x less than or e qual to 0.39 ceramic samples. Careful analysis of the temperature and oxygen content dependence shows a complex behaviour of the magnetic fi eld at the muon site. The two main novelties are that a) the muon does not diffuse freely above 250 K, as previously stated, and that b) mob ile holes phase separate, inducing a finite size reduction of the AF o rder parameter.