Abstract
Spectral ellipsometry is used to determine the dielectric function of an untwinned crystal of in the range 0.5–5.6 eV at temperatures . A pronounced redistribution of spectral weight is found at the Néel temperature . The anisotropy of the spectral weight transfer matches the magnetic ordering pattern. A superexchange model quantitatively describes spectral weight transfer induced by spin correlations. This analysis implies that the lowest-energy transitions around 2 eV are intersite - transitions, and that is a Mott-Hubbard insulator.
- Received 17 May 2004
DOI:https://doi.org/10.1103/PhysRevLett.93.147204
©2004 American Physical Society