Cobalt nanoparticles with preferential hcp structure: A confirmation by X-ray diffraction and NMR

Матвеев, В. В.; Баранов, Д. А.; Yurkov, G. Yu.; Akatiev, Nikita G.; Dotsenko, I. P.; Губин, С. П.

doi:10.1016/j.cplett.2006.02.099

Cited by 69 publications

(36 citation statements)

References 14 publications

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“…27 However, based on experimental results for hcp nanoparticles, an assignment of 225.5 MHz is reasonable. 29 As can be seen in Fig. 6, the 59 Co NMR spectrum for the CoTe(1) films is characterized by a broad peak with apparently two structural components; the components clearly do not match peaks associated with domain walls in the fcc or hcp phases.…”

Section: Discussionmentioning

confidence: 86%

Direct evidence for the source of reported magnetic behavior in “CoTe”

et al. 2017

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In order to unambiguously identify the source of magnetism reported in recent studies of the Co-Te system, two sets of high-quality, epitaxial CoTex films (thickness ≈ 300 nm) were prepared by pulse laser deposition (PLD). X-ray diffraction (XRD) shows that all of the films are epitaxial along the [001] direction and have the hexagonal NiAs structure. There is no indication of any second phase metallic Co peaks (either fcc or hcp) in the XRD patterns. The two sets of CoTex films were grown on various substrates with PLD targets having Co:Te in the atomic ratio of 50:50 and 35:65. From the measured lattice parameters c = 5.396 Å for the former and c = 5.402 Å for the latter, the compositions CoTe1.71 (63.1% Te) and CoTe1.76 (63.8% Te), respectively, are assigned to the principal phase. Although XRD shows no trace of metallic Co second phase, the magnetic measurements do show a ferromagnetic contribution for both sets of films with the saturation magnetization values for the CoTe1.71 films being approximately four times the values for the CoTe1.76 films. 59 Co spin-echo nuclear magnetic resonance (NMR) clearly shows the existence of metallic Co inclusions in the films. The source of weak ferromagnetism reported in several recent studies is due to the presence of metallic Co, since the stoichiometric composition "CoTe" does not exist.

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Section: Discussionmentioning

confidence: 86%

Direct evidence for the source of reported magnetic behavior in “CoTe”

et al. 2017

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“…Os resultados sugeriram que o uso do óxido de trifenilfosfina como o segundo surfactante propiciou a obtenção de nanopartículas monodispersas [36]. A decomposição térmica do (Co(HCOO) ) foi também utilizada por Matveev e 2 colaboradores para a obtenção de nanopartículas de cobalto com a estrutura hcp dispersas em politetrafluoroetileno [42]. A decomposição térmica do octacarbonil de dicobalto em tolueno também foi empregada por Yin e Wang, entretanto, utilizando o bis(2-etilexil)sulfoccinato de sódio como agente para evitar a aglomeração das partículas.…”

Section: Nanopartículas De Cobalto: Sínteses E Caracterizaçõesunclassified

Nanopartículas magnéticas: o cobalto

Sargentelli

Ferreira

2010

Eclet. Quim.

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The development of nanoparticles has been intensively pursued because of their technological importance. The magnetic nanoparticulate materials exhibit a series of interesting properties between which are mentioned the electrical, optical, magnetic and chemical properties. Magnetic nanostructures can be used in microelectronic and in medicine as in: magnetic memory storage, magnetic transport of biochemical complexes, magnetic resonance imaging, among others. The magnetic properties of nanoparticles there are very sensitive to its size and form. In this direction, many efforts they have been carried through with the intention of to control the form and distribution of the size of the nanoparticles. In the last few decades nanoparticles constituted by iron oxides had been studied. However, more recently, the focus of the researches has come back to others transitions metals. Amongst these, the cobalt comes being investigated due to its high magnetic susceptibility. In this context, the present article has the aim of to presents and to effect a comparative analysis of the more significant synthetic ways utilized in the present moment to obtain cobalt nanoparticles.

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“…A spectrum of the "Co" sample was already detected previously at 77 K [2] and indicated the main signal near 226 MHz corresponded to metallic cobalt in the form of hcp phase. A spectrum of the "FeCo" sample is displayed in figure 2, and shows metallic cobalt as well, mostly in the hcp phase also.…”

Section: Nmr and Mössbauer Datamentioning

confidence: 99%

“…Nanocomposites under study were prepared by the method of thermal decomposition as described earlier, see [2] and references within. An average diameter of the particles was about 10 nm, a total cobalt concentration was equal to 5 mass.% in both samples, and iron concentration was 5 mass.% in the "FeCo" samples.…”

Section: Methodsmentioning

confidence: 99%

“…In the simple case of uniaxial anisotropy a magnetic moment of nanoparticle (that is the case for Co one [2]) is aligned along this axis and without an external magnetic field both directions of magnetization in the anisotropy axis are equivalent, while at presence of field one of them is preferred. After the field switching off the magnetization should mount the energy barrier E b = KV (K is an anisotropy constant, and V is a volume of particle) to rotate back to the state defined by anisotropy, which takes a time.…”

Section: Second Harmonic Of Magnetization Datamentioning

confidence: 99%

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Study of Magnetic Nanocomposites by NMR and Bulk Magnetization Techniques

Матвеев

Ryzhov

Lashkul

et al. 2014

EPJ Web of Conferences

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Abstract. Magnetic nanocomposites possess complex and nonuniform magnetic structure. As a result it is necessary to use different physical methods to describe their properties. In this work we have applied a combination of micro and macro approaches to understand more deeply magnetic properties of some cobaltcontaining nanocomposites. Testing of magnetic structure of the samples at molecular level was done with NMR and Mössbauer techniques whereas static (SQUID) and dynamic magnetic (M 2 , see below) measurements -at macro level.

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Cobalt nanoparticles with preferential hcp structure: A confirmation by X-ray diffraction and NMR

Cited by 69 publications

References 14 publications

Direct evidence for the source of reported magnetic behavior in “CoTe”

Direct evidence for the source of reported magnetic behavior in “CoTe”

Nanopartículas magnéticas: o cobalto

Study of Magnetic Nanocomposites by NMR and Bulk Magnetization Techniques

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