Charge ordering in half-doped manganites

Alternative descriptions for the ground state structure of the half-doped manganite Pr_0.5Ca_0.5MnO₃ have been tested against high-resolution 10 K x-ray and neutron powder diffraction data. The best fit is obtained using a P2₁∕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 Pnm2₁ pseudosymmetry, used to describe Zener polaron ordering in Pr_0.6Ca_0.4MnO₃ [ Phys. Rev. Lett. 89 097205 (2002)], gives a different, bistriped, charge and orbitally ordered model that does not fit the data as well.