  The temperature-concentration phase diagram of the Si-doped spin-Peierls
compound CuGeO$_{3}$ is investigated by means of neutron scattering and muon
spin rotation spectroscopy in order to determine the microscopic distribution
of the magnetic and lattice dimerised regions as a function of doping. The
analysis of the zero-field muon spectra has confirmed the spatial inhomogeneity
of the staggered magnetisation that characterises the antiferromagnetic
superlattice peaks observed with neutrons. In addition, the variation of the
macroscopic order parameter with doping can be understood by considering the
evolution of the local magnetic moment as well as of the various regions
contributing to the muon signal.
