Spin-phonon coupling in Mn-Bi co-doped SmFeO3: An experimental study

•Polycrystalline Sm0.9Bi0.1Fe0.9Mn0.1O3 is synthesized using solid-state reaction.•An AFM behavior with weak FM is observed below TN ~ 620 K.•The oxidation state of elements is validated by X-ray photoemission core level spectra.•Signature of spin-phonon coupling is seen in terms of phonon anomaly below the TN. The intriguing physical properties of SmFeO3 such as spin-phonon coupling and spin reorientation transition (~480 K) make it interesting from fundamental point of view and a suitable candidate for oxide-based spintronic applications. Here, we have studied the temperature dependent structural, vibrational, and magnetic properties of polycrystalline Sm0.9Bi0.1Fe0.9Mn0.1O3 prepared by conventional solid-state reaction method. The compound stabilizes in orthorhombic structure with space group “Pnma” and exhibits no structural phase transitions in the investigated temperature range (300–500 K). Magnetic measurements reveal the weak ferromagnetic–paramagnetic transition at 620 K. Thermal evolution of phonon modes investigated using Raman spectroscopy in the temperature range 300–800 K reveal that Ag(3) phonon mode related to FeO6 vibrations exhibits anomalous behaviour below magnetic transition temperature, which we attribute to spin-phonon coupling. The optical band gap value of ∼ 5.17 eV has been estimated from the analysis of UV–Vis diffuse reflectance spectroscopy using the Tauc relation. The value of ΔEt2u→t2g is estimated to be ~ 2.6 eV for p-d charge transfer transitions in Fe/MnO6 octahedra. The obtained valence states from X-ray photoelectron spectroscopy analysis of all the elements of the sample are in excellent agreement with the expected values.