Evidence for a distributed ferromagnetic transition in (La,Ca)MnO3

We report new zero-field mu SR measurements in ferromagnetic (FM) (La,Ca)MnO3 which are consistent with two spatially separated regions in close proximity possessing very different Mn-ion spin dynamics. We present a picture in which one region corresponds to an extended spin polaron which displays a peak in the relaxation rate near the Curie temperature T-c and an increasing volume fraction below T-c. The second region possesses slower fluctuating spins and a decreasing volume fraction below T-c. These data suggest a microscopically inhomogeneous FM phase transition resulting From the overlap of spin polarons. (C) 2000 Elsevier Science B.V. All rights reserved.