Local structural distortions in manganites probed by comparative x-ray-emission and x-ray-absorption near-edge measurements

Document Type

Article

Publication Date

1-1-2001

Abstract

Comparison studies of the perovskite compounds system R1-xCaxMnO3 (R=La, Bi) by both Mn Kβ-emission spectroscopy and x-ray-absorption near-edge spectroscopy (XANES) are presented. The insensitivity of x-ray-emission measurements to structural distortions coupled with the sensitivity of x-ray-absorption near-edge measurements to changes in both structure and valence enable one to detect the presence of structural distortions, such as local Jahn-Teller (JT) distortions. Theoretical XANES computations for pure cubic perovskite and locally distorted endmembers are used to show the effect of distortions on XANES spectra as well as to comment on the nature of the pre-edge features in the spectra. We show by explicit computations that the near-edge spectra are determined by dipole transitions while pure 1s to 3d electric quadrupole transitions determine a very limited section of the pre-edge region. Simulations of the pre-edge features reveal a direct connection between local distortions and the a1 feature amplitude. The Bi-containing system is found to have significantly higher levels of distortions than the La system. XANES studies of the AMnO3 (A=La, Pr, and Nd) system reveal a direct relationship between the main line width and the magnitude of the JT distortions.

Identifier

4243686904 (Scopus)

Publication Title

Physical Review B Condensed Matter and Materials Physics

External Full Text Location

https://doi.org/10.1103/PhysRevB.64.024430

ISSN

01631829

First Page

244301

Last Page

244307

Issue

2

Volume

64

Grant

9802513

Fund Ref

National Science Foundation

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