Spin-controlled mott-hubbard bands in LaMnO3 probed by optical ellipsometry -: art. no. 147204

Spectral ellipsometry is used to determine the dielectric function of an untwinned crystal of LaMnO3 in the range 0.5-5.6 eV at temperatures 50less than or equal toTless than or equal to300 K. A pronounced redistribution of spectral weight is found at the Neel temperature T-N=140 K. 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 d-d transitions, and that LaMnO3 is a Mott-Hubbard insulator.