Commensurate-incommensurate transition in the melting process of orbital ordering in Pr0.5Ca0.5MnO3: A neutron diffraction study - art. no. 212407

The melting process of the orbital order in Pr0.5Ca0.5MnO3 single crystal h as been studied in detail as a function of temperature by neutron diffracti on. It is demonstrated that a commensurate-incommensurate (C-IC) transition of the orbital ordering takes place in a bulk sample, being consistent wit h the electron diffraction studies. The lattice structure and the transport properties go through drastic changes in the IC orbital ordering phase bel ow the charge/orbital ordering temperature T-CO/OO, indicating that the ano malies are intimately related to the partial disordering of the orbital ord er, unlike the consensus that it is related to the charge disordering proce ss. For the same T range, partial disorder of the orbital ordering turns on the ferromagnetic spin fluctuations which were observed in a previous neut ron scattering study.