1/18/2024 0 Comments Activity diagrams thermodynamics![]() ![]() ![]() There seems an incompatible contradiction for iron oxide clusters to bear high stability and strong ferromagnetism. However, the antiferromagnetic states were often found to be much more stable than the ferromagnetic counterparts 61, 62. Reasonable research interest has been devoted to polynuclear clusters 46, 47, 48, 49, 50, especially the magic-number iron clusters and iron oxide clusters such as a ring cluster Fe 10 (ref. It has been recognized that the magnetic moments of metal clusters depend on geometry and electron localization 44, 45. Notably, iron atoms in most of these oxide clusters, except a few (FeO) n clusters 23, are separated by oxygen atoms but without direct Fe–Fe bonds, resulting in a tendency of antiferromagnetic rather than ferromagnetic properties. Studies of such unique stoichiometries not only elucidate varying electronic and geometric structures of iron oxides 36, but also provide fundamental information on the kinetics and thermodynamics of coordination and catalytic reactions 37, 38, 39, 40, 41, 42, 43. 32) clusters have been extensively studied 33, 34, 35. 16, 17, 18) and oxygen-rich clusters 19, 20, 21, 22, as well as sequential stoichiometries of (FeO) m (ref. Meanwhile, oxo, peroxo, and superoxo isomers 15, dioxygen, and oxygen complexes Fe(O 2) n (refs. Typically, FeO is antiferromagnetic at low temperatures but with a high-spin 5Δ ground state based on the DFT-GGA calculations 14 Fe 2O 3 is antiferromagnetic but Fe 3O 4 is known to be ferrimagnetic. Iron compounds could exhibit a variety of magnetic properties, with appropriate nuclearity and topology to function as molecular magnets 12, 13. On the premise and aim of a full understanding of the spin-exchange interactions and structure-property relationship 7, 8, ongoing continuous efforts have also been devoted to understanding the gas-phase reactivity of such clusters 9, as well as fundamental mechanisms and potential applications relating to metalloenzymes and metallic corrosion and catalysis 10, 11. Sub-nano clusters of iron oxides could exhibit altered properties in comparison with larger nanoparticles, enabling highly tuneable magnetism and chemical activity, and thus are ideal candidates for high-density storage or spintronics microdevices when embedded in semiconductors. ![]() Magnetic iron oxide nanoparticles are well-known for their significance in targeted drug delivery 1, 2, 3, magneto-responsive therapy and multimodal imaging, as well as microwave-absorption and magneto-optical crossover applications 4, 5, 6. ![]()
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