Ab initio x-ray absorption study of the manganese K-edge XANES spectra in Mn- and Zn-related hexagonal perovskites

摘要

An x-ray absorption spectroscopy study of several Mn-containing one-dimensional-related hexagonal perovskites BaMnO_3, Ca_3ZnMnO_6, and Sr_4ZnMn_2O_9 is reported. A combined analysis of the Mn K-edge extended x-ray absorption fine structure and x-ray absorption near-edge structure has been conducted to investigate a possible disordering caused by the cation interchange between crystallographic lattice sites. For Ca_3ZnMnO_6 and Sr_4ZnMn_2O_9 compounds, ab initio computations based on multiple-scattering theory suggest that Mn is present at two different crystallographic sites: in addition to the expected MnO_6 octahedra, Mn stands also in the trigonal prism site. This cation disordering would explain satisfactorily the observed temperature magnetic behavior of Sr_4ZnMn_2O_9.