Magnetic Properties and Mössbauer Spectroscopy of Fe₃O₄/CoFe₂O₄ Nanorods

Fe₃O₄/CoFe₂O₄ nanorods were obtained via a simple seed-mediated synthesis. Nanorods were used as seeds to grow CoFe₂O₄ by thermal codecomposition of the cobalt(II) and iron(III) acetylacetonate precursors. The growth process was monitored by electron microscopy (SEM, TEM), and the resulting nanorods were characterized by powder X-ray diffraction analysis and IR and Raman spectroscopy. Magnetometry and AC susceptometry studies revealed a distribution of Néel relaxation times with an average blocking temperature of 140 K and a high-field magnetization of 42 Am²/kg. Complementarily recorded ⁵⁷Fe-Mössbauer spectra were consistent with the Fe₃O₄/CoFe₂O₄ spinel structure and exhibited considerable signs of spin frustration, which was correlated to the internal and surface structure of the nanorods.