Тип публикации: статья из журнала
Год издания: 2013
Идентификатор DOI: 10.1007/s11051-012-1397-0
Ключевые слова: Iron sulfides Fe3S4, Magnetic and electronic properties, Mossbauer spectroscopy, Magnetic circular dichroism, Blocking temperature, Cation vacancies, Covalencies, D-d transitions, Electron excitations, Fast electrons, Fe-ions, Ferrimagnetic behavior, Greigites, Iron ions, Iron sulfide, Isostructural, Magnetic circular dichroisms, Magnetic field dependences, Mossbauer, Non-stoichiometric, Optical spectra, Preparation conditions, Small particles, Spinel-type, Ssbauer spectroscopies, Superparamagnetic behavior, Superparamagnetic phase, Verwey transitions, Wide-band, Alcohols, Electronic properties, Iron, Iron compounds, Magnetic moments, Metal ions, Nanoparticles, Particle size analysis, Spectroscopy, Sulfur compounds, Superparamagnetism, Synthesis (chemical), ferrous sulfide, iron sulfide nanoparticle, nanoparticle, polyol, unclassified drug, article, chemical structure, circular dichroism, covalent bond, electric conductivity, electron, electronics, magnetic field, magnetism, particle size, priority journal, room temperature, stoichiometry, synthesis, X ray diffraction
Аннотация: Iron sulfide nanoparticles Fe3S4 with the spinel-type crystal structure were synthesized by the polyol mediated process. The particle size depends on preparation conditions and varies from 9 to 20 nm. Mossbauer data have revealed that the dominating fraction of iron ions in the 9-nm sample is in the high-spin ferric state. This implies an occurrence of the cation vacancies in nonstoichiometric greigite. The stoichiometric phase of greigite Fe3S4 dominates in the 18-nm-size nanoparticles. Magnetic measurements have shown a ferrimagnetic behavior of all samples at temperatures between 78 and 300 K. The estimated value of magnetic moment of the stoichiometric greigite nanoparticles is about 3.5 mu(B) per Fe3S4 unit. The Mossbauer spectra indicate a superparamagnetic behavior of small particles, and some fraction of superparamagnetic phase is observed in all samples synthesized which may be caused by the particle size distribution. The blocking temperatures of T-B approximate to 230 and 250 K are estimated for the 9 and 14 nm particles, respectively. The Mossbauer parameters indicate a great degree of covalency in the Fe-S bonds and support the fast electron Fe3+ reversible arrow Fe2+ exchange in the B-sites of greigite. An absence of the Verwey transition at temperatures between 90 and 295 K is established supporting a semimetal type of conductivity. The temperature and magnetic field dependences of the magnetic circular dichroism (MCD) of optical spectra were measured in Fe3S4 for the first time. The spectra differ substantially from that of the isostructural oxide Fe3O4. It is supposed that the MCD spectra of greigite nanoparticles result from the collective electron excitations in a wide band with superimposed peaks of the d-d transitions in Fe ions.
Журнал: JOURNAL OF NANOPARTICLE RESEARCH
Выпуск журнала: Vol. 15, Is. 1
ISSN журнала: 13880764
Место издания: DORDRECHT
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