Phase separation and ferroelectric ordering in charge-frustrated

Abstract: The transmission electron microscopy observations of the charge ordering (CO) which governs the electronic polarization in clearly show the presence of a remarkable phase separation at low temperatures. Two CO ground states are found to adopt the charge modulations of and , respectively. Our structural study demonstrates that the incommensurately -modulated state is chiefly stable in samples with relatively lower oxygen contents. Data from theoretical simulations of the diffraction suggest that both - and -modulated phases have ferroelectric ordering. The effects of oxygen concentration on the phase separation and electric polarization in this layered system are discussed. [Copyright &y& Elsevier]