Charge ordering in half-doped manganites

Alternative descriptions for the ground state structure of the half-doped manganite Pr0.5Ca0.5MnO3 have been tested against high-resolution 10 K x-ray and neutron powder diffraction data. The best fit is obtained using a P2(1)/m symmetry model, which supports the striped charge and orbital ordering picture. The magnitude of the charge ordering is, however, only 25% of the ideal Mn3+/Mn4+ separation. An alternative Pnm2(1) pseudosymmetry, used to describe Zener polaron ordering in Pr0.6Ca0.4MnO3 [Phys. Rev. Lett. 89, 097205 (2002)], gives a different, bistriped, charge and orbitally ordered model that does not fit the data as well.