2003/05/31 by S. Grenier, J. P. Hill, Doon Gibbs +9
Chemistry · Materials Science · Physics and Astronomy · #Ab initio #Advanced Condensed Matter Physics #Chemistry #Condensed matter physics #Crystallography #Diffraction #Magnetic and transport properties of perovskites and related materials #Materials science #Order (exchange) #Perovskite (structure) #Physics #Quantum mechanics #Rare-earth and actinide compounds #Spectral line #Type (biology) #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.69.134419
15 pages, 15 figures
arxiv created 2004/01/19 · openalex publication_date 2004/04/15 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report a resonant x-ray-diffraction study of the magnetoresistant perovskite Pr0.6Ca0.4MnO3. We discuss the spectra measured above and below the semiconductor-insulator transition temperature with the aid of a detailed formal analysis of the energy and polarization dependences of the structure factors and ab initio calculations of the spectra. In the low-temperature insulating phase, we find that inequivalent Mn atoms order in a CE-type pattern and that the crystallographic structure of La0.5Ca0.5MnO3 [Radaelli et al., Phys. Rev. B 55, 3015 (1997)] can also describe this system in detail. Instead, the alternative structure proposed for the so-called Zener-polaron model [Daoud-Aladine et al., Phys. Rev. Lett. 89, 097205 (2002)] is ruled out by crystallographic and spectroscopic evidence. Our analysis supports a model involving orbital ordering. However, we confirm that there is no direct evidence of charge disproportionation in the Mn K-edge resonant spectra. Therefore, we consider a CE-type model in which there are two Mn sublattices, each with partial eg occupancy. One sublattice consists of Mn atoms with the 3x2\ensuremath-r2 or 3y2\ensuremath-r2 orbitals partially occupied in an alternating pattern, the other sublattice with the x2\ensuremath-y2 orbital partially occupied.