Magnetic properties and structural analysis on spinel MnFe₂O₄ nanoparticles prepared via non-aqueous microwave synthesis

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Simon, Christopher ; Blößer, André ; Eckardt, Mirco ; Kurz, Hannah ; Weber, Birgit ; Zobel, Mirijam ; Marschall, Roland:
Magnetic properties and structural analysis on spinel MnFe₂O₄ nanoparticles prepared via non-aqueous microwave synthesis.
In: Zeitschrift für anorganische und allgemeine Chemie. Bd. 647 (2021) Heft 22 . - S. 2061-2072.
ISSN 1521-3749
DOI: https://doi.org/10.1002/zaac.202100190

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Abstract

Phase-pure 6 nm spinel MnFe₂O₄ nanoparticles with high specific surface area of 145 m² g−1 were successfully prepared via microwave-assisted non-aqueous sol-gel synthesis. The phase evolution during postsynthetic thermal treatment was investigated systematically by various methods, including powder X-ray diffraction (PXRD), pair distribution function (PDF) analysis, and Raman spectroscopy. Our results show that the material decomposes to non-spinel binary compounds α-Mn₂O₃ and α-Fe₂O₃ at temperatures between 400 and 600 °C. The application potential of MnFe₂O₄ nanoparticles with 3d⁵ Mn(II) and Fe(III) ions with respect to the magnetic properties was demonstrated by superconducting quantum interference device (SQUID) magnetometry, with the as-synthesized nanoparticles reaching a high saturation magnetization of 2.62 μB per formula unit (63.5 Am² kg−1) at 10 K. We further highlight the visible-light response of synthesized powders, making the materials promising for light-related applications, e. g. photocatalytic hydrogen evolution. An important additional feature of MnFe₂O₄ nanoparticles is their good dispersibilty in polar or non-polar media, as a result of postsynthetic colloidal stabilization with betaine hydrochloride, oleic acid combined with oleylamine, or citric acid.