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Raman evidence for orbiton-mediated multiphonon scattering in multiferroic TbMnO3
Pradeep Kumar1, Surajit Saha, D V S Muthu
1Department of Physics, Indian Institute of Science, Bangalore-560012, India.
Summary
This study reveals that high-frequency Raman bands in Terbium Manganite (TbMnO3) exhibit mixed orbiton-phonon characteristics. Anomalous softening of a phonon mode below the Néel temperature indicates strong spin-phonon coupling.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Spectroscopy
Background:
- Terbium Manganite (TbMnO3) is a multiferroic material exhibiting complex magnetic and electronic properties.
- Understanding the interplay between spin, lattice, and orbital degrees of freedom is crucial for novel material design.
Purpose of the Study:
- To investigate the temperature-dependent behavior of Raman spectra in TbMnO3.
- To elucidate the nature of high-frequency Raman modes and their relationship with magnetic ordering.
- To identify evidence of spin-phonon coupling in TbMnO3.
Main Methods:
- Temperature-dependent Raman spectroscopy was performed on TbMnO3 samples.
- Measurements were conducted across a temperature range of 5 to 300 K.
- Raman spectra were analyzed in the 200-1525 cm(-1) range.
Main Results:
- Five first-order Raman allowed phonon modes and two high-frequency modes were observed.
- The high-frequency Raman band displayed a constant and high intensity ratio (∼0.6) with a first-order mode, suggesting an orbiton-phonon mixed nature.
- Anomalous softening of a first-order phonon mode was detected below the Néel temperature (T(N) ≈ 46 K).
Conclusions:
- The high-frequency Raman modes in TbMnO3 are characterized by a mixed orbiton-phonon nature.
- The observed anomalous phonon softening below T(N) provides strong evidence for significant spin-phonon coupling in TbMnO3.
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