Influence of Rare Earth Yb3+ Dopant on the Spectroscopic Properties of Manganese Ferrite Nanoparticles

A series of MnFe_2–xYb_xO₄ powder nanoparticles (for x = 0, 0.025, 0.075, 0.1, and 0.2) of different crystallite sizes were synthesised using the co-precipitation method. The effect of Yb³⁺ dopant on the properties of manganese ferrite was characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman measurements, and photoluminescence spectroscopy (PL). The crystallite size and density of the samples have a cubic structure with an Fd3m space group. Their sizes and densities were found to be in the range of 24.8–34.7 nm and 5.07–5.49 g/cm³. FT-IR analysis indicates the presence of two absorption bands in the range 400–600 cm^–1, which is a fingerprint region of ferrites. The v₂ band (Fe–O stretching mode of the octahedral site) shifts towards the lower wavenumber, which confirms the occupancy of larger-size Yb³⁺ ions at the octahedral site. The Raman peaks were noted at 228, 295, 405, 502, and 634 cm^–1 for undoped manganese ferrite. Based on Raman observations, it has been observed that Mn²⁺ ions exhibit a preference for occupying octahedral (B) sites by substituting Fe³⁺ ions. Additionally, rare earth ions have been preferentially observed to occupy octahedral sites. The primary cause for the displacement of Raman bands was ascribed predominantly to the greater radii of rare earth ions in comparison with Fe³⁺ and Mn²⁺ ions, and the shifting of the peaks indicates the presence of Yb³⁺ at the octahedral site. The PL spectrum shows emission at 560 nm with a rise in intensity with an increase in dopant Yb³⁺, which could be because of the incorporation of Yb³⁺ in the spinel structure, leading to radiative recombination in the yellow region of the electromagnetic spectrum.