Charge ordering in half-doped manganites

Abstract

Alternative descriptions for the ground state structure of the half-doped manganite ${\mathrm{Pr}}_{0.5}{\mathrm{Ca}}_{0.5}\mathrm{Mn}{\mathrm{O}}_{3}$ have been tested against high-resolution $10\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ x-ray and neutron powder diffraction data. The best fit is obtained using a $P{2}_{1}∕m$ symmetry model, which supports the striped charge and orbital ordering picture. The magnitude of the charge ordering is, however, only 25% of the ideal ${\mathrm{Mn}}^{3+}∕{\mathrm{Mn}}^{4+}$ separation. An alternative $Pnm{2}_{1}$ pseudosymmetry, used to describe Zener polaron ordering in ${\mathrm{Pr}}_{0.6}{\mathrm{Ca}}_{0.4}\mathrm{Mn}{\mathrm{O}}_{3}$ [Phys. Rev. Lett. 89, 097205 (2002)], gives a different, bistriped, charge and orbitally ordered model that does not fit the data as well.