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. The observed anomalies in phonon frequency, linewidth, and intensity near the phase transition temperatures highlight the importance of lattice–charge–spin interactions in SmBaMn2O6.