Zener polaron ordering in half-doped manganites -: art. no. 097205

We have refined the crystal structures of a Pr0.60Ca0.40MnO3 single crystal from neutron diffraction data. The result at low temperature gives a superstructure that cannot be interpreted as Mn3+/Mn4+ charge ordering. The pattern of atom displacements suggests the trapping of electrons within pairs of Mn sites, involving both a local double exchange and a polaronic-like distortion. The two mechanisms act together to form vibronic localized electronic states: Zener polarons. We have confirmed this picture by showing how it elucidates the unconventional paramagnetic behavior of half-doped manganites.