Raman and infrared study of 4f electron-phonon coupling in HoVO3

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spectroscopy

Background:

• RVO3 (R = Ho, Y) compounds exhibit complex phase transitions influenced by V(3+) orbitals, magnetic moments, and crystal structure.
• Understanding spin-phonon coupling and ion-ligand field interactions is crucial for characterizing their physical properties.

Purpose of the Study:

• To investigate first-order Raman scattering and multiphonons in HoVO3 and YVO3 across different crystallographic phases.
• To analyze infrared transmittance to understand electronic excitations and their coupling with lattice vibrations.
• To correlate spectroscopic findings with magnetic ordering and crystallographic transitions.

Main Methods:

• Temperature-dependent Raman scattering measurements.
• Temperature-dependent infrared transmittance spectroscopy.
• Analysis of phonon anomalies and electronic excitations.

Main Results:

• Similar Raman spectral features observed in HoVO3 and YVO3 due to similar R-ion radii.
• Anomalous phonon shifts linked to spin-phonon coupling below the magnetic ordering temperature (T N1 ≈ 110 K).
• Exclusive phonon anomalies in HoVO3 around T* ≈ 15 K and distinct transition temperatures (T N2) for magnetic/orbital reorientations (40 K for HoVO3, 77 K for YVO3).
• Infrared transmittance revealed Ho(3+) excitations and vibronics, with drastic changes at T N2 indicating strong Ho(3+)-ligand field coupling.

Conclusions:

• Spin-phonon coupling significantly influences phonon behavior in RVO3 systems below magnetic ordering.
• HoVO3 exhibits unique phonon anomalies and strong Ho(3+)-ligand field interactions, correlating with its magnetocaloric properties.
• The study elucidates the interplay between magnetic, orbital, and structural degrees of freedom in RVO3 compounds.