  The emergence of superlattice periodicities at metal to insulator transitions
in hole doped perovskite oxides responds to a rearrangement of the local atomic
structure, and electron and spin density distribution. Originally, the ionic
model based on a checkerboard- type atomic distribution served to describe the
low temperature charge and orbital ordered (COO) phases arising in half- doped
manganites. In the last years, the exploitation of resonant x- ray scattering
(RXS) capabilities has shown the need to revisit these concepts and improve the
picture. Yet, we have realised that COO is a more common phenomenon than
expected that can be observed in a wide range of doping levels. Here we compare
the experimental data recently collected by RXS on La_0.4Sr_1.6MnO_4 (x=0.60)
and La(Pr)_1/3Sr_2/3FeO_3 (x=0.67). The first shows a COO phase similar to that
found in the x=0.5 sample but angular peak positions vs. T denotes the
incommensurability of superlattice reflections. Meanwhile, the analysis of the
commensurate CO phase in the studied ferrite underlines the role of the
structural changes also involving La(Sr) and O atoms.
