The anelastic spectra of ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ have been measured at liquid-He temperatures slightly below and above the concentration $x_c\simeq 0.02,$ which is considered to separate the spin-glass phase from the cluster spin-glass (CSG) phase. For $x<~x_c,$ all the elastic energy-loss functions show a step below the temperature $T_g\mathrm{}(x=0.02\mathrm{})\mathrm{}$ of freezing into the CSG state, similar to what is found in samples well within the CSG phase, but with a smaller amplitude. The excess dissipation in the CSG state is attributed to the motion of the domain walls between the clusters of antiferromagnetically correlated spin. These results are in agreement with the recent proposal, based on inelastic neutron scattering, of an electronic phase separation between regions with $x\sim 0$ and $x\sim 0.02,$ at least for $x>\mathrm{}\mathrm{0.015.}\mathrm{}$

• Received 15 February 2002

DOI:https://doi.org/10.1103/PhysRevB.66.094503