In orthorhombic SmMn2O5 single crystals, Sm3+ crystal-field (CF) excitations are studied by infrared transmission as a function of temperature and under applied magnetic field up to 10 T. These measurements are complemented with the study of Raman-active phonon frequency shifts as a function of temperature between 300 and 5 K. The frequencies of all Hj6 crystal-field levels of Sm3+ were determined as well as those of Fj6. At high temperatures, the evolutions of Sm3+ CF excitations exhibit anomalies around the characteristic temperatures, T∗∼60K and TS∼120K and reflect the thermal disorder induced by splitting of the Sm-O bonds in SmMn2O5 that contribute to the frequency and linewidth phonon shifting. At low temperatures, the degeneracy of the ground-state Kramers doublet is lifted (Δ0∼36cm-1) due to the Sm3+-Mn3+ interaction in the ferroelectric phase and strongly enhanced below TC∼26K. The Sm-Mn exchange interaction J6 is determined and compared to that of Gd-Mn interaction in GdMn2O5. The Sm magnetic moment mSm(T) and the Sm contribution to the magnetic susceptibility are also evaluated from Δ0(T), indicating that the Sm-Mn interaction is strongly implicated in the magnetic and the ferroelectric orderings below ∼26K. The study of the Sm3+ CF excitations as a function of magnetic field reveals twinning in SmMn2O5. This twinning could affect its electric polarization behavior versus magnetic field.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics