Raman studies of lattice-charge-spin coupling in double perovskite SmBaMn₂O₆

The complex phase transitions of SmBaMn₂O₆ single crystals are investigated using temperature-dependent Raman spectroscopy. Distinct anomalies associated with the charge-orbital ordering are observed in the breathing mode at 614 cm⁻¹, which shows a pronounced enhancement at the high-temperature charge-orbital ordering temperature of 380 K and a splitting into 597 and 631 cm⁻¹ at the low-temperature charge-orbital ordering temperature of 200 K. Furthermore, the Jahn-Teller mode at 480 cm⁻¹ exhibits a blueshift up to 5 cm⁻¹ below the antiferromagnetic spin ordering temperature of 175 K, indicating spin-phonon interaction with a strong coupling constant of 2.5 cm⁻¹.