Crossover from dilute to majority spin freezing in two leg ladder system Sr(Cu, Zn)2O3

Muon spin relaxation has been measured in Sr(Cu1-xZnx)(2)O-3. The results for low Zn concentration x less than or equal to 0.6% are consistent with freezing of dilute moments, with one Cu spin for each Zn, having similar to 0.5 mu(B) frozen moment. A sharp increase of the relaxation rate at T --> 0 occurred with increasing x around x similar or equal to 0.8%, accompanied by a change of line shape to that expected in a concentrated magnetic environment. Analyses of the results for x greater than or equal to 0.8% suggest that the majority of Cu moments participate in spin freezing, yet with a significantly reduced and spatially inhomogeneous moment size having a 1D correlation length xi similar to 6 lattice units, or a 2D correlation area involving similar to 19 Cu spins.