  Charge and orbital ordering behaviors in the half doped bi-layered compound
LaSr2Mn2O7 have been studied by resonant and non-resonant X-ray scattering.
Three different order parameters, which correspond to the A-type
antiferromagnetic, a charge and an orbital ordered states, were observed by
measuring the magnetostriction and the superlattice peaks characterized by
wavevectors (1/2 1/2 0) and (1/4 1/4 0), respectively. The superlattice
reflections indicating the charge and orbital ordered states were observed
below 210 K. Both the intensities reach a maximum at 160 K on cooling and
become very weak below 100 K. The peak width of the charge ordered state agrees
with that of the orbital ordered state at all temperatures studied. These
results indicate that both the states originate from a single phase and that
the charge/orbital ordered islands with definite interfaces disperse in the
A-type antiferromagnetic phase. The dimensionality of the charge/orbital
ordered phase is discussed using this model.
