Direct Imaging of Nanoscale Phase Separation in La(0.55)Ca(0.45)MnO(3): Relationship to Colossal Magnetoresistance

Abstract

A nanoscale phase is known to coexist with colossal magnetoresistance (CMR) in manganites, but its volume fraction is believed to be too small for a causal connection. Here we provide nanodiffraction real-space images of nanoclusters that form and evolve with temperature in La1-xCaxMnO3, x = 0.45. The nanoclusters are not doping inhomogeneities; their structure corresponds to x = 0.60, at which the bulk material at low temperatures is antiferromagnetic, �charge-ordered�, and insulating; and their volume ratio exhibits a large peak at the CMR critical temperature at finite magnetic fields, suggesting a zero-field volume fraction of ~ 35 %. These features are sufficient to account for the CMR peak. We propose that the phenomenon arises from an interplay of magnetic and structural entropies.