Abstract
The geometric and electronic local structure of LaMnO3 across the cooperative Jahn–Teller (JT) transition at TJT = 750 K has been studied by means of X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) at the Mn K-edge. XANES spectra, as a function of temperature, do not show significant changes either in the pre-peak structures or at the absorption edge indicating similar electronic local structure for the Mn atom above and below TJT. Analysis of the EXAFS spectra shows that dynamical tetragonal JT distortion of the MnO6 octahedron is also present above TJT. The structural transition is explained in terms of an orientated ordering of tetragonal distorted octahedral complexes. Above TJT, the eg electron jumps between the three degenerate vibronic states being localized and ordered below the transition.
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