Observation of Two Time Scales in the Ferromagnetic Manganite La1−xCaxMnO3, x≈0.3

Abstract

We report new zero-field muon spin relaxation and neutron spin echo measurements in ferromagnetic (FM) $(\mathrm{La},\mathrm{Ca}){\mathrm{MnO}}_3$ which suggest at least two spatially separated regions possessing very different Mn-ion spin dynamics. One region displays diffusive relaxation, “critical slowing down” near $T_C$ and an increasing volume fraction below $T_C$, suggesting overdamped FM spin waves below $T_C$. The second region possesses more slowly fluctuating spins, a linewidth independent of $q$, and a decreasing volume fraction below $T_C$. The estimated length scale for the inhomogeneity is $\le 30Å$.