Polaron lifetime in La_0.75Ca_0.25MnO₃

As part of continuing effort to accurately characterize the nature of the polaron in perovskite manganese oxides, quasielastic neutron scattering measurements were performed on a single-crystal sample of La_0.75Ca_0.25MnO₃. Energy scans at the wavevector for the short-range correlation peak in the paramagnetic insulator phase show that the line widths are resolution-limited at all temperatures. In contrast, the line width of the diffuse part of the scattering due to uncorrelated polarons was found to be much larger, as large as 4 meV (FWHM), and of the same order of magnitude as that of magnetic scattering. Results of the measurements are interpreted on the basis of a scattering function consisting of terms for isolated polarons and for polarons in clusters.