While being key to understanding their intriguing physical properties, the origin of nanophase separation in manganites and other strongly correlated materials is still unclear. Here, experimental evidence is offered for the origin of the controverted phase separation mechanism in the representative La1-x
system. For low hole densities, direct evidence of Mn4+ holes localization around Ca2+ ions is experimentally provided by means of aberration-corrected scanning transmission electron microscopy combined with electron energy loss spectroscopy. These localized holes give rise to the segregated nanoclusters, within which double exchange hopping between Mn3+
remains restricted, accounting for the insulating character of perovskites with low hole density. This localization is explained in terms of a simple model in which Mn4+ holes are bound to substitutional divalent Ca2+
Nano Lett., 2016
Figure 1. HAADF images along (a)  and (b)  corresponding to La0.9Ca0.1MnO3. The basic perovskite (ABO3) unit cell has been marked in yellow in both images. At the bottom, schematic models for the cationic position and enhanced details of the HAADF images have been inserted. Among A columns, atomic columns of different brightness, better perceived from a distance, reflecting different La and Ca occupations are arrowed in green and yellow, respectively.