Spin-controlled Mott-Hubbard bands in LaMnO_3 probed by optical ellipsometry

TL;DR

This study uses spectral ellipsometry to investigate the dielectric properties of LaMnO_3, revealing spin-controlled spectral weight redistribution and confirming its nature as a Mott-Hubbard insulator.

Contribution

It provides the first detailed optical analysis of LaMnO_3's spectral weight transfer related to magnetic ordering and supports a superexchange model for spin correlations.

Findings

Spectral weight redistributes at the Neel temperature.

Anisotropy matches magnetic ordering pattern.

Transitions around 2 eV are intersite d-d transitions.

Abstract

Spectral ellipsometry has been used to determine the dielectric function of an untwinned crystal of LaMnO_3 in the spectral range 0.5-5.6 eV at temperatures 50 K < T < 300 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 LaMnO_3 is a Mott-Hubbard insulator.