Characterization of Magnetic Phases in Nanostructured Ferrites by Electron Spin Resonance

Díaz-Pardo, Rebeca; Valenzuela, R.

doi:10.5772/61508

Cited by 10 publications

(11 citation statements)

References 32 publications

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“…The position of resonance i.e. effective g -value was calculated to be 2.005 for the GSH-CoFe 2 O 4 MNPs, a value that is typical for paramagnetic compounds [49]. Upon conjugation of the GSH-CoFe 2 O 4 MNPs with the Pcs (using CoFe 2 O 4 - 1 as an example), there was a slight reduction in the intensity of the spectrum, suggesting that the magnetic behaviour of the MNPs slightly decreased after conjugation.…”

Section: Resultsmentioning

confidence: 99%

Dual phototransformation of the pollutants methyl orange and Cr (VI) using phthalocyanine-cobalt ferrite based magnetic nanocomposites

Mapukata

Osifeko

Nyokong

2019

Heliyon

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Bifunctional nanocomposites based on zinc phthalocyanines and glutathione capped CoFe 2 O 4 magnetic nanoparticles (GSH-CoFe 2 O 4 MNPs) are applied in a binary system wherein simultaneous photooxidation of methyl orange (MO) and photoreduction of Cr (VI) are conducted. The photoactivity of two zinc Pcs with different functional moieties are compared based on their interactions with GSH-CoFe 2 O 4 MNPs. Conjugation of the Pcs to the GSH-CoFe 2 O 4 MNPs not only enhanced their singlet oxygen production but also their photocatalytic activity in both photooxidation and photoreduction experiments. Using electron paramagnetic resonance (EPR) spectroscopy, the Pc-MNP conjugates reported herein were found to exhibit superparamagnetic behaviour, giving the advantage of easy separation using an external magnetic field post application, an attractive attribute for heterogeneous catalysis. The catalysts reported herein are therefore good candidates as catalysts for real life water purification analyses as they facilitate the treatment of both organic and inorganic water pollutants.

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Section: Resultsmentioning

confidence: 99%

Dual phototransformation of the pollutants methyl orange and Cr (VI) using phthalocyanine-cobalt ferrite based magnetic nanocomposites

Mapukata

Osifeko

Nyokong

2019

Heliyon

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“…The spins are identical, and the material becomes antiferromagnetic. The low Néel temperature clearly illustrates the weakness of this superexchange interaction, as compared with A-O-B of the nickel ferrite case [5].…”

Section: Introductionmentioning

confidence: 91%

“…The end compositions are zinc ferrite, ZnFe 2 O 4 (for x = 0), i.e., a direct spinel, and nickel ferrite, NiFe 2 O 4 (x = 1), an inverse spinel. In direct spinel ZnFe 2 O 4 , the behavior is antiferromagnetic with a Néel temperature about 9 K, while for nickel ferrite is ferrimagnetic with a Curie point about T = 860 K [5]. The possibility to control the chemical composition allows to finely tailor the magnetic features.…”

Section: Introductionmentioning

confidence: 99%

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Raman spectroscopy in Zinc Ferrites Nanoparticles

Galinetto¹,

Albini²,

Bini³

et al. 2018

Raman Spectroscopy

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ZnFe 2 O 4 ferrite nanoparticles are arousing a great interest in the biomedical field, thanks to their superparamagnetic behavior at room temperature. Functional properties depend on composition, size, nanoparticle architecture and, in turn, on the synthesis methods. Bulk ZnFe 2 O 4 has the normal spinel structure (all Zn 2+ ions in tetrahedral and all Fe 3+ ions in octahedral positions), but at the nanometric size inversion takes place with a cationic mixing on divalent and trivalent sites. The sensitivity of the Raman probe to cation disorder favored the appearance of several works on a rich variety of nanosized zinc ferrites. An overview on these results is reported and discussed at variance with synthesis methods, grain dimensions, and dopants. We add to this landscape our results from new nanosized powder samples made by microwave-assisted combustion, with different dopants (Ca, Sr on Zn site and Al, Gd on Fe site). A detailed analysis of A 1g , E g , 3F 2g Raman modes has been performed and Raman band parameters have been derived from bestfitting procedures and carefully compared to literature data. The vibrational results are discussed taking into account the characterization from X-ray powder diffraction raction, SEM-EDS probe, EPR spectroscopy and, of course, the magnetic responses.

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“…The high frequency edge of the resonance is broader and exhibits a lower intensity than the initial one. The inhomogeneous broadening behaviour is common in nanoparticle systems [26,27] due to the existence of higher order spin-wave modes, that can be originated from different ways: interaggregate dipolar interaction due to large residual strains, porosity or inhomogeneities in the sample, random distributions of anisotropy axis [25], as well as increased losses caused by hopping of conduction electrons that enhances the relaxation, when the particle size is small compared with the skin depth [27]. In the Figure 8a, we show the broadening factor calculated as the ratio among minimum and maximum in the derivative of the absorption curve.…”

Section: Microwave Characterizationmentioning

confidence: 99%

Synthesis, structural characterization and broadband ferromagnetic resonance in Li ferrite nanoparticles

Hernández-Gómez

Graça

Muñoz

2018

Journal of Alloys and Compounds

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Lithium ferrites are well known materials due to its numerous technological applications especially in microwave devices. Lithium ferrite nanoparticles were prepared by sol-gel technique by means of Pechini method, and then annealed at different temperatures in 250-1000º C range. XRD confirms spinel formation with particles sizes in 15-700 nm range, with increased size with annealing temperature, whereas FTIR and Raman measurement confirm that single phase lithium ferrite with ordered cationic structure is obtained. Microwave magnetoabsorption data of the annealed lithium ferrite nanoparticles were obtained with a broadband system based on a network analyzer that operates up to 8.5 GHz. At fields up to 200 mT we can observe a broad absorption peak that shifts to higher frequencies with magnetic field according to ferromagnetic resonance theory. The amplitude of absorption, up to 85 %, together with the frequency width of about 5.5 GHz makes this material suitable as wave absorber. FMR parameters like resonance field, linewidth and broadening are analyzed in order to obtain the characteristic parameters and analyze the microwave behaviour.

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Characterization of Magnetic Phases in Nanostructured Ferrites by Electron Spin Resonance

Cited by 10 publications

References 32 publications

Dual phototransformation of the pollutants methyl orange and Cr (VI) using phthalocyanine-cobalt ferrite based magnetic nanocomposites

Dual phototransformation of the pollutants methyl orange and Cr (VI) using phthalocyanine-cobalt ferrite based magnetic nanocomposites

Raman spectroscopy in Zinc Ferrites Nanoparticles

Synthesis, structural characterization and broadband ferromagnetic resonance in Li ferrite nanoparticles

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