Observation of two time scales in the ferromagnetic manganite La(1-x)Ca(x)MnO(3), x = 0.3

TL;DR

This study reveals two distinct spin dynamic regions in ferromagnetic La(1-x)Ca(x)MnO(3), indicating a microscopically inhomogeneous transition driven by polaron growth, as shown by muon spin relaxation and neutron spin echo measurements.

Contribution

It provides the first evidence of spatially separated spin dynamic regions in ferromagnetic manganite, highlighting inhomogeneity in the magnetic transition.

Findings

Identification of a critical slowing down near Tc in one region.

Observation of slowly fluctuating spins decreasing below Tc.

Evidence of inhomogeneous ferromagnetic transition due to polaron growth.

Abstract

We report new zero-field muon spin relaxation and neutron spin echo measurements in ferromagnetic (FM) (La,Ca)MnO3 which taken together suggest two spatially separated regions in close proximity possessing very different Mn-ion spin dynamics. One region corresponds to an extended cluster which displays 'critical slowing down' near Tc and an increasing volume fraction below Tc. The second region possesses more slowly fluctuating spins and a decreasing volume fraction below Tc. These data are discussed in terms of the growth of small polarons into overlapping regions of correlated spins below Tc, resulting in a microscopically inhomogeneous FM transition.