Charge-transfer transitions in mixed-valent multiferroic TbMn2O5
Abstract
Optical response of mixed-valent manganite TbMn2O5 is studied in the spectral range from 0.6to5.8eV in order to reveal the charge-transfer (CT) transitions responsible for the band-gap structure. Strong increase of optical response for the z and y polarizations and strong anisotropy with a relation γ2x<γ2y<γ2z are found. These findings agree with the theoretical analysis derived from the orientation of the Mn3+O5 pyramids in the unit cell and points to the one-center p-d CT transitions as the main contributors to the spectral weight. We argue that the CT processes are accompanied by giant electric-dipole fluctuations and therefore may be a source of large electric polarization of Mn3+O5 pyramids due to the parity-breaking Mn3+-Mn4+ isotropic exchange interaction.
- Publication:
-
Physical Review B
- Pub Date:
- February 2008
- DOI:
- 10.1103/PhysRevB.77.060102
- Bibcode:
- 2008PhRvB..77f0102M
- Keywords:
-
- 78.20.Ci;
- 75.47.Lx;
- 71.20.Ps;
- Optical constants;
- Manganites;
- Other inorganic compounds