MEM Charge Density Analysis of Orbital-Ordering of Nd_0.35Sr_0.65MnO₃

抄録

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 600 K (>>T_N=260 K). Consistently, we observed an anisotropic charge density distribution around the Mn ion at 30 K (<<T_N), indicating the long-range ordering of the d_3z²−r² orbital. At 300 K (≥T_N), however, the charge density distribution becomes isotropic, suggesting the disappearance of the long-range orbital ordering.