We report on longitudinal field (LF) mu SR measurements of the dynamic magn
etic properties of the Gd moments in GdBa2Cu3O6+x as a function of the oxyg
en content. It is shown that the observed increase of the depolarization ra
te with decreasing oxygen content can be explained by the change in populat
ion of the two mu(+) stopping sites in GdBa2Cu3O6+x samples. The observed s
tretched exponential depolarization function is shown to be the result of a
n anisotropic second moment of the field distribution at the muon positions
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