Role of the A-site size and oxygen stoichiometry in charge ordering commensurability of Ln0.50Ca0.50MnO3 manganites

The structures of the Ln0.50Ca0.50MnO3 manganites (Ln = Pr, Nd, Sm, Eu and Gd) are studied using electron diffraction and lattice imaging. Results show that the tendency to form an incommensurate structure at temperatures below 92 Kelvin increases with increasing lanthanide size. A transition towards a commensurate state is also observed for the smaller cations Nd, Sm, Eu and Gd with further cooling.