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Spin-controlled Mott-Hubbard bands in LaMnO3 probed by optical ellipsometry
N N Kovaleva1, A V Boris, C Bernhard
1Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
Physical Review Letters
|November 5, 2004
Summary
Spectral ellipsometry reveals that lanthanum manganite (LaMnO3) undergoes significant spectral weight changes at its Neel temperature. These changes, linked to spin correlations, confirm LaMnO3 as a Mott-Hubbard insulator.
Area of Science:
- Solid State Physics
- Materials Science
- Magnetism
Background:
- Lanthanum manganite (LaMnO3) is a complex oxide exhibiting intriguing electronic and magnetic properties.
- Understanding the interplay between electronic transitions and magnetic ordering is crucial for materials science.
Purpose of the Study:
- To investigate the dielectric function and electronic transitions in LaMnO3 using spectral ellipsometry.
- To correlate observed spectral weight changes with magnetic ordering and spin correlations.
Main Methods:
- Spectral ellipsometry was employed to measure the dielectric function of untwinned LaMnO3 crystals.
- Measurements were conducted over a wide spectral range (0.5-5.6 eV) and temperature range (50-300 K).
Main Results:
- A significant redistribution of spectral weight was observed at the Neel temperature (T(N) = 140 K).
- The anisotropy of spectral weight transfer was found to align with the magnetic ordering pattern.
- A superexchange model successfully quantified the spectral weight transfer driven by spin correlations.
Conclusions:
- The study confirms LaMnO3 as a Mott-Hubbard insulator.
- The lowest-energy electronic transitions around 2 eV are identified as intersite d-d transitions, influenced by magnetic ordering.