The Mössbauer spectra of precipitation-obtained Fe3O4 recorded at 290, 240, 180, 160,120 and 80 K

For the preparation of Fe₃O₄ (sample S2), aqueous solutions of iron(II) and iron(III) chlorides were used as precursors, maintaining the molar ratio Fe²⁺/Fe³⁺ = 1/2. Under continuous stirring, NH₄OH (25 wt.% aqueous solution) was added dropwise until the final pH reached 10.5–11.0, promoting the formation of magnetite. The resulting precipitate was then aged under the same conditions as in the S1 synthesis, after which the solid product was separated by centrifugation, washed repeatedly with distilled water to remove residual salts and unreacted species, and dried at 85–95 °C until constant mass, yielding the Fe₃O₄ material. To obtain additional information on the structural and phase composition of the synthesized Fe₃O₄, low-temperature Mössbauer spectroscopy was applied. The Mössbauer spectra of sample S2 were recorded at 290, 240, 180, 160,120 and 80 K, enabling assessment of the Fe²⁺/Fe³⁺ distribution and hyperfine parameters characteristic of magnetite, as well as their temperature-dependent behavior.