Direct evidence for cobalt substitution effects in magnetite

Sorescu, Monica; Oberst, Thomas E.; Gossett, K; Tarabasanu, D.; Diamandescu, L.

doi:10.1016/s0038-1098(99)00540-2

Cited by 14 publications

(4 citation statements)

References 12 publications

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“…The absorption percentage, close to 2 %, observed in all Mössbauer spectra is comparable with the value reported for Sorescu and coworkers [18] in Co 2+ substituted magnetites obtained by the hydrothermal method, however it is lower than the absorption percentage reported by da Costa and coworkers [19] in pure magnetites. In our case, the low absorption could be attributed to a non optimal selection of the 14.4 keV signal in the pulses discriminator of the Mössbauer spectrometer, however the counting statistic of the spectra was significant in order to obtain a satisfactory signal to noise ratio and have a good fitting in all spectra.…”

Section: Mössbauer Spectroscopysupporting

confidence: 89%

Influence of Co2+ on the structural and magnetic properties of substituted magnetites obtained by the coprecipitation method

Velasquez

Urquijo

2015

Hyperfine Interact

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In this paper we report the effect of divalent cobalt on the structural and magnetic properties of substituted magnetites, Fe 3−x Co x O 4 , with γ =Co 2+ /Fe= 0, 5, 10, 15, 20 and 30 % wt, synthesized by the coprecipitation method. The samples were characterized by Atomic Absorption Spectroscopy, X-ray Diffraction, room temperature Mössbauer Spectroscopy and Vibrating Sample Magnetometry. The effect of Co 2+ was found to depend strongly of the concentration employed in the synthesis process. For γ ≤15 % the Co 2+ promotes the formation of particles more crystalline and with higher saturation magnetization, remanence and coercivity than those obtained in absence of this cation. A sequential increasing of the lattice parameter is observed, as well as a reduction in the hyperfine magnetic field of the Fe 2.5+ sub spectrum, while the hyperfine magnetic field of the Fe 3+ sub spectrum keeps almost constant. For γ =20 % and 30 % the crystallinity of the samples decreases, particle size distribution effects are evidenced and the saturation magnetization decreases drastically. The results suggest that for low Co 2+ contents the substitution of Fe 3+ by Co 2+ at octahedral sites of the inverse spinel system is the dominant effect, while for the highest concentrations used the substitution of Fe 2+ by Co 2+ and the increasing of the particle size distribution are the dominant effects.

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Section: Mössbauer Spectroscopysupporting

confidence: 89%

Influence of Co2+ on the structural and magnetic properties of substituted magnetites obtained by the coprecipitation method

Velasquez

Urquijo

2015

Hyperfine Interact

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“…24 Unfortunately, most particles produced are below the SD limit, it uses expensive toxic chemicals and high temperatures ($200 C), so requires specialised equipment and is not environmentally friendly. [24][25][26]29 Hydrothermal methods involve partial oxidation of ferrous hydroxide (POFH) by addition of nitrate and a base and heating to $90 C. 24,27,28 This method allows tuning of MNP size and composition, but increased temperature and precise control over reaction conditions are required to achieve this. 24 Room temperature co-precipitation (RTCP) of cobalt-doped magnetite from an Fe 2+ /Fe 3+ /Co 2+ salt solution occurs under an inert atmosphere when base is added at ambient temperature and pressure.…”

Section: Preliminary Nanoparticle Synthesis and Characterisationmentioning

confidence: 99%

“…Methods for synthesising precise MNPs often require careful control of reaction conditions, toxic chemicals and high temperatures. [24][25][26][27][28][29] As such, they are expensive, difficult to scale up to industrial production and environmentally harmful. Cruder methods that are cheaper and use more environmentally friendly chemicals, such as co-precipitation, produce a wide range of sizes and shapes of MNPs.…”

Section: Introductionmentioning

confidence: 99%

Magnetic bacterial protein Mms6 controls morphology, crystallinity and magnetism of cobalt-doped magnetite nanoparticles in vitro

et al. 2011

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“…The authors argue that it is not possible to know where copper cations are incorporated in the structure. Sorescu, Oberst, Gosset, Tarabasanu and Diamandescu [13][14][15] synthesized hydrothermally samples of magnetite doped with Co 2+ in percentages from 0 to 60 atm.% and characterized the samples by room temperature Mössbauer spectroscopy. Their results showed that Co 2+ is incorporated preferentially in the octahedral sites, because the magnetic hyperfine field increased appreciably in these sites while remained almost constant in the tetrahedral sites, and the area of the octahedral sub spectrum decreased.…”

Section: Introductionmentioning

confidence: 99%

Study of the Effect of Cu<sup>2+</sup> in the Lattice Dynamics of Doped Magnetites Obtained by the Hydrothermal Synthesis Method

Velasquez¹,

Urquijo²

2013

SAR

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In this work, the effect of Cu 2+ on the structural and magnetic properties of samples of magnetite is addressed. Samples of magnetite, both pure and Cu 2+ doped, Fe 3-x Cu x O 4 , with x = 0, 5, 10 and 20 atm.% were synthesized hydrothermally. The two-lattice method was employed to measure the Mössbauer recoilless fraction of magnetite relative to hematite (f mag /f hem ) of the samples, looking for evidence of substitution of Fe 2+ by Cu 2+ . The relative recoilless fraction measurements were performed by taking room temperature Mössbauer spectra of mixtures of each sample with analytical grade hematite. The Mössbauer measurements were complemented with Atomic Absorption Spectroscopy (AAS) and Energy Dispersive X-ray Spectroscopy (EDS). The analyses by AAS and EDS showed that the copper concentration in the final products increases with increasing the content of Cu 2+ in the starting solutions. The Mössbauer analyses showed a linear decrease trend of the relative Mössbauer recoilless fraction with increasing concentration of Cu 2+ in the samples, as well as a reduction in the hyperfine magnetic field, which was more significant in the octahedral sites than tetrahedral sites. The broadening of the Mössbauer spectral lines was more significant for the octahedral sub spectrum than for the tetrahedral sub spectrum. Our study points that Cu 2+ occupies preferentially the octahedral sites, where it substitutes Fe 2+ species, generating broadening in the lines of the octahedral sub spectrum and a reduction in the probability of having nuclear resonant absorption of Mössbauer gamma rays in the samples.

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Direct evidence for cobalt substitution effects in magnetite

Cited by 14 publications

References 12 publications

Influence of Co2+ on the structural and magnetic properties of substituted magnetites obtained by the coprecipitation method

Influence of Co2+ on the structural and magnetic properties of substituted magnetites obtained by the coprecipitation method

Magnetic bacterial protein Mms6 controls morphology, crystallinity and magnetism of cobalt-doped magnetite nanoparticles in vitro

Study of the Effect of Cu<sup>2+</sup> in the Lattice Dynamics of Doped Magnetites Obtained by the Hydrothermal Synthesis Method

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Direct evidence for cobalt substitution effects in magnetite

Cited by 14 publications

References 12 publications

Influence of Co2+ on the structural and magnetic properties of substituted magnetites obtained by the coprecipitation method

Influence of Co2+ on the structural and magnetic properties of substituted magnetites obtained by the coprecipitation method

Magnetic bacterial protein Mms6 controls morphology, crystallinity and magnetism of cobalt-doped magnetite nanoparticles in vitro

Study of the Effect of Cu&lt;sup&gt;2+&lt;/sup&gt; in the Lattice Dynamics of Doped Magnetites Obtained by the Hydrothermal Synthesis Method

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Study of the Effect of Cu<sup>2+</sup> in the Lattice Dynamics of Doped Magnetites Obtained by the Hydrothermal Synthesis Method