Crossover from dilute to majority spin freezing in two leg ladder system Sr(Cu, Zn)(2)O-3

Muon spin relaxation has been measured in Sr(Cu1-xZnx)(2)O-3. The results f or low Zn concentration x less than or equal to 0.6% are consistent with fr eezing 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 b y a change of line shape to that expected in a concentrated magnetic enviro nment. 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 si gnificantly reduced and spatially inhomogeneous moment size having a 1D cor relation length xi similar to 6 lattice units, or a 2D correlation area inv olving similar to 19 Cu spins.