Resonant scattering and multiple Bragg X-ray diffraction in LaMnO3; a classical view.
The mechanism for resonant scattering in LaMnO(3) has been the subject of some controversy between two models. Model (A) is based on orbital ordering, whereas model (B) invokes the Jahn-Teller distortion. From the structural point of view, the two models lead to different d-electron densities. The forbidden reflection 300 is turned on by resonance, leading to a well defined scheme for the lobes of the Mn d electrons [model (A)]. It turns out that the same experimental results could have been interpreted according to model (B). The only difference is that this alternative interpretation would have required a structure factor F(300) of opposite sign. This is a typical example of a phase problem. An experimental technique has been applied for phase determination based on multiple Bragg scattering. This shows that the multiple-beam results are in agreement with model (B), not with model (A), laying to rest a long overdue controversy.
Colella
Roberto
R
Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907-2036, USA. colella@physics.purdue.edu
Shen
Qun
Q