Evidence for charge and orbital order in the doped titanates   RE_(1-x)Ca_xTiO_3 (RE=Y, Er, Lu)
  Combining macroscopic and diffraction methods we have studied the electric, magnetic and struc- tural properties of RE_(1-x)Ca_xTiO_3 (RE=Y, Er, Lu) focusing on the concentration range near the metal-insulator transition. The insulating phase, which is stabilized by a smaller rare-earth ionic ra- dius, exhibits charge order with a predominant occupation of the dxy orbital. The charge and orbital ordering explains the broad stability range of the insulating state in RE_(1-x)Ca_xTiO_3 with smaller rare-earth ions. The strong modulation of the Ti-O bond distances indicates sizeable modulation of the electric charge. 
A. C. Komarek, M. Reuther, T. Lorenz, A. Cousson, P. Link, W.   Morgenroth, D. Trots, C. Baehtz, and M. Braden
cond-mat.str-el