The anelastic spectra (elastic energy loss and dynamic modulus versus temperature) of ${\mathrm{La}}_{1-x}{\mathrm{Ca}}_x{\mathrm{MnO}}_3$ have been measured for $0.33<x<\mathrm{}\mathrm{0.5.}\mathrm{}$ A peak in the imaginary part of the elastic susceptibility is found slightly below the Curie temperature, whose temperature and frequency dependences are typical of the dielectric and magnetic susceptibilities of relaxor ferroelectrics, spin glasses and other inhomogeneous frustrated systems. The fluctuations can be associated with the magnetic clusters which are observed by several techniques or with charge-ordered insulating domains in the low temperature inhomogeneous phase. The temperature dependent distribution function of the fluctuation energy barriers has been extracted by an analysis of the experimental curves.

• Received 18 September 2001

DOI:https://doi.org/10.1103/PhysRevB.65.012403