Ferromagnetic Ordering and Unusual Magnetic Ion Dynamics in La0.67Ca0.33MnO3

Zero-field muon spin relaxation and resistivity experiments on La0.67Ca0.33MnO3 powder show that the sublattice magnetization νμ(T) is well described for T≤Tc by (1-TTc)β, where β=0.345±0.015, characteristic of a second-order phase transition for a 3D spin system, and the ferromagnetic transition temperature (Tc=274 K) and resistivity peak temperature coincide to within 1 K. Below TCνμ and the zero-field resistivity ρ are correlated, with νμ∝-lnρ. Unusual relaxational dynamics suggest spatially inhomogeneous Mn-ion correlation times. These results are discussed in terms of the possible effects of polarons on the spin and charge dynamics.