Raman spectroscopy probed spin-two phonon coupling and improved magnetic and optical properties in Dy and Zr substituted BiFeO3 nanoparticles

In this study BiFeO3 (BFO), Bi0.9Dy0.1FeO3 (BDFO) and Bi0.9Dy0.1Fe0.97Zr0.03O3 (BDFZO) nanoparticles were prepared by sol-gel route. X-ray diffraction study showed rhombohedral structure for BFO while orthorhombic structure for BDFO and BDFZO samples. X-ray photoelectron spectroscopy indicated the dominancy of Fe3+ oxidation state in BDFO sample which decreases in BDFZO sample. All samples showed ferromagnetic behaviour with saturation magnetization of 0.5, 5.5 and 5.2 emu/g for BFO, BDFO and BDFZO samples, respectively. A slight decrease in magnetization for BDFZO sample as compared to BDFO sample may be attributed to the substitution of non-magnetic Zr4+ ion which does not take part directly in magnetization. Two-phonon Raman mode located at ∼1260 cm−1 showed anomalous intensity in pure BFO which subsequently suppressed for BDFO and BDFZO samples indicating spin-two phonon coupling in these samples. UV-Visible diffuse spectroscopy results showed that the band-gap of BFO, BDFO and BDFZO samples were 2.26, 2.22 and 2.24 eV, respectively, suitable for photocatalytic applications.