MEM charge density analysis of orbital-ordering of Nd_0.35Sr _0.65MnO₃

The charge density distribution of Nd_0.35Sr _0.65MnO₃ has been investigated by means of the maximum entropy method (MEM) using the synchrotron radiation (SR) X-ray powder diffraction data. In this compound, the anisotropic optical spectra reported by Tobe et al. [Phys. Rev. B 67 (2003) 140402(R)] suggest that the d _3z2-r2 orbital-ordering survives even at 600K (≫ T_N = 260 K). Consistently, we observed an anisotropic charge density distribution around the Mn ion at 30K (≪ T_N), indicating the long-range ordering of the d_3z2-r2 orbital. At 300K (≥ T_N), however, the charge density distribution becomes isotropic, suggesting the disappearance of the long-range orbital ordering.