ON SPIN HAMILTONIAN FITS TO MÖSSBAUER SPECTRA OF NiFe2O4 NANOPARTICLES SYNTHESIZED BY CO-PRECIPITATION

Jose Higino Dias Filho, Jorge Luis López Aguilar, Adriana Silva de Albuquerque, Renato Dourado Maia, Wesley de Oliveira Barbosa, Ernando Campos Ferreira, Fellipe Silva Pereira, Kátia Ferreira Guimarães Benfica

Resumo


Nanocrystalline NiFe2O4 particles prepared by chemical co-precipitation method were studied using magnetic measurements, 57Fe Mössbauer spectroscopy, X-ray diffraction, and transmission electron microscopy. Fits to Mössbauer spectra, in the range of 4.2 K – 300 K, were done using spin hamiltonians to describe both the electronic and nuclear interactions, a model of superparamagnetic relaxation of two levels (spin ½) and stochastic theory, a log-normal particle size distribution function as well as a dependency of the magnetic transition temperature and the anisotropy constant on particle diameter. We have used evolutionary strategies to fit the more complex Mössbauer spectra line shapes. The nanoparticles have an average size of 7 nm and exhibit superparamagnetism at room temperature. The saturation magnetization (Ms) at 4.2 K was determined from M vs. 1/H plots by extrapolating the value of magnetizations to infinite fields, to 24.21 emu/g and coercivity to 3.15 kOe. A magnetic anisotropy energy constant (K) 1.9´105 J/m3, at 4.2 K, were calculated from magnetization measurements. The synthesis, characterization, and functionalization of magnetic nanoparticles is a highly active area of current research located at the interface between materials science, biotechnology, and medicine. Superparamagnetic iron oxides nanoparticles have unique physical properties and have emerged as a new class of diagnostic probes for multimodal tracking and as contrast agents for magnetic resonance imaging (MRI).

Palavras-chave


NiFe2O4 nanoparticles; Evolutionary strategies; Fits on Mössbauer spectra

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DOI: http://dx.doi.org/10.21575/25254782rmetg2020vol5n61339

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Direitos autorais 2020 Jose Higino Dias Filho, Jorge Luiz Lopez, Adriana Silva de Albuquerque, Renato Dourado Maia, Wesley de Oliveira Barbosa, Ernando Campos Ferreira, Fellipe Silva Pereira, Kátia Guimarães Benfica

Revista Mundi Engenharia, Tecnologia e Gestão ISSN 2525-4782

Qualis: B4 - Interdisciplinar, B5 - Geografia, B5 - Administração Pública e de Empresas, Ciências Contábeis e Turismo, B5 - Comunicação e Informação, B5 - Engenharias III