High-temperature charge-ordering fluctuation in manganites

High-temperature (T) studies of La1-xCaxMnO3 show that charge and phonon transport is significantly suppressed in a narrow doping region of x approximate to1/2 and in a wide T range up to 900 K, which accompanies anomalous broadening of x-ray Bragg peaks. Contrarily, ferromagnetic (FM) correlation above Curie T is sharply enhanced at x approximate to3/8. All these observations indicate the presence of short-range charge ordering (CO) correlation at high T, possibly in the form of a FM ``zigzag,{''} a small segment of the CE-type CO state. The decoupling and coupling of the FM zigzags for x approximate to3/8 and 1/2, respectively, is consistent with our results.