Commensurate-incommensurate phase transition in charge ordered La _1-xCa_xMnO₃ by single crystal diffraction and electron imaging

Electron nanodiffraction from single crystal domain of La _1-xCa_xMnO₃ with 0.5 ≤ x ≤ 0.8 is carried out to study the charge ordering phase transition in this system. The melting processes of charge ordering structure in samples with x = 1/2, 2/3 and 4/5 are observed in-situ by increasing temperature from 93K - 298K. During the phase transition, electron diffraction results show that the nearly commensurate low-temperature charge ordering structure continuously evolves to incommensurate structure with directly decreasing sizes of charge ordered area. The picture of this phase transition is confirmed by the real space imaging. The real space images clearly show the introduction of charge ordering defects during the melting process in this sample.