Study of crystal-field excitations and infrared active phonons in TbMnO.

The Tb (4f ) crystal-field (CF) excitations and the infrared phonons in TbMnO are studied as a function of temperature and under an applied magnetic field. The phonon energy shifts reflect local displacement of the oxygen ions that contribute to the CF energy level shifts below 120 K and under magnetic field. The CF polarized transmission spectra provide interesting information about the debated nature of the excitations at 41, 65, 130 cm.

A comparative Raman study between PrMnO , NdMnO , TbMnO and DyMnO .

In this paper, we present a detailed Raman study of the non-multiferroic compounds PrMnO and NdMnO and the multiferroic compounds TbMnO and DyMnO as a function of temperature and magnetic field. All studied systems show anomalous phonon shifts close to the Néel transition T . In PrMnO and NdMnO , the frequency softenings are partly attributed to an orbital-spin-phonon coupling whereas in TbMnO and DyMnO , the relatively weak frequency shifts are rather attributed to an expansion of the Mn-O bond lengths.

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

First-order Raman scattering and multiphonons are studied in RVO3 (R  =  Ho and Y) as a function of temperature in the orthorhombic and monoclinic phases. Raman spectra of HoVO3 and YVO3 unveil similar features since both compounds have nearly identical R-radii. However, the most important difference lies in the transition temperature involving the V(3+) orbitals, the V(3+) magnetic moments as well as the crystallographic structure.

Micro-Raman and infrared studies of multiferroic TbMn₂O₅.

We have studied the Raman and infrared spectral response of TbMn2O5 under an applied magnetic field parallel to the easy magnetic a-axis at 4.2 K. Strong spin-lattice coupling in TbMn2O5 is evidenced by a frequency shift of Raman and infrared phonons as a function of magnetic field compared to the phonon response of BiMn2O5 that remains unaffected.

Study of crystal-field excitations and infrared active phonons in the multiferroic hexagonal DyMnO3.

In hexagonal DyMnO3, Dy(3+) crystal-field excitations are studied as a function of temperature and applied magnetic field. They are complemented with the measurements of infrared active phonon frequency shifts under applied magnetic field at T = 4.2 K.