| 1. |
- González-Alonso, David, et al.
(författare)
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Identifying the presence of magnetite in an ensemble of Iron-oxide nanoparticles : A comparative Neutron diffraction study between bulk and nanoscale.
- 2021
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Ingår i: Nanoscale Advances. - : RSC. - 2516-0230. ; 3, s. 3491-
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Tidskriftsartikel (refereegranskat)abstract
- Scientific interest in iron–oxides and in particular magnetite has been renewed due to the broad scope of its fascinating properties, which are finding applications in electronics and biomedicine. Specifically, iron oxide nanoparticles (IONPs) are gathering attraction in biomedicine. Their cores are usually constituted by a mixture of maghemite/magnetite phases. In view of this, to fine-tune the properties of an ensemble of IONPs towards their applications, it is essential to enhance mass fabrication processes towards the production of monodispersed IONPs with controlled size, shape, and stoichiometry. We exploit the vacancy sensitivity of the Verwey transition to detect the presence of magnetite. Here we are providing a direct evidence of the Verwey transition in an ensemble of IONPs through neutron diffraction. This transition is observed as a variation in the Fe moment at the octahedral sites and, in turn, gives rise to a change of the net magnetic moment. Finally, we show this variation as the microscopic ingredient driving the characteristic kink that hallmarks the Verwey transition in thermal variation of magnetization.
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| 2. |
- González-Alonso, David, et al.
(författare)
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Revealing a masked Verwey transition in nanoparticles of coexisting Fe-oxide phases
- 2021
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Ingår i: RSC Advances. - : The Royal Society of Chemistry. ; 11:1, s. 390-396
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Tidskriftsartikel (refereegranskat)abstract
- The attractive electronic and magnetic properties together with their biocompatibility make iron-oxide nanoparticles appear as functional materials. In Fe-oxide nanoparticle (IONP) ensembles, it is crucial to enhance their performance thanks to controlled size, shape, and stoichiometry ensembles. In light of this, we conduct a comprehensive investigation in an ensemble of ca. 28 nm cuboid-shaped IONPs in which all the analyses concur with the coexistence of magnetite/maghemite phases in their cores. Here, we are disclosing the Verwey transition by temperature dependent (4–210 K) Raman spectroscopy.
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| 3. |
- Gonzalez-Alonso, David, et al.
(författare)
-
Revealing a masked Verwey transition in nanoparticles of coexisting Fe-oxide phases
- 2020
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 11:1, s. 390-396
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Tidskriftsartikel (refereegranskat)abstract
- The attractive electronic and magnetic properties together with their biocompatibility make iron-oxide nanoparticles appear as functional materials. In Fe-oxide nanoparticle (IONP) ensembles, it is crucial to enhance their performance thanks to controlled size, shape, and stoichiometry ensembles. In light of this, we conduct a comprehensive investigation in an ensemble of ca. 28 nm cuboid-shaped IONPs in which all the analyses concur with the coexistence of magnetite/maghemite phases in their cores. Here, we are disclosing the Verwey transition by temperature dependent (4-210 K) Raman spectroscopy.
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| 4. |
- Jefremovas, Elizabeth M., et al.
(författare)
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Dual disorder-driven magnetic dynamics in GdCu2 superantiferromagnetic nanoparticles
- 2022
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Ingår i: Journal of nanoparticle research. - : Springer Nature. - 1388-0764 .- 1572-896X. ; 24:10
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Tidskriftsartikel (refereegranskat)abstract
- The spin dynamics in magnetically disordered GdCu2 nanoparticles, varying the nanoparticle size in the range 53 to 7 nm, has been scrutinized. Dynamic chi(AC) susceptibility measurements have revealed the existence of dissipation at T-g = 18 K, which is associated to the spin freezing transition, for all the ensembles. Besides, the superantiferromagnetic ensembles (< D & rang;>= 24 nm) also showcase a dissipation contribution close to the vicinity of the Neel transition, T-N = 40.2 K. This dissipation, which takes the form of two humps located at T-d1 = 33.5(5) K and T-d2 = 40.0(5) K, is associated to uncompensated antiferromagnetic moments. Time-dependent phenomena (ageing and memory effects) are only evidenced below the spin freezing transition, evidencing that solely this low-temperature disordered phase is driven by the frustration of RKKY exchange interactions. Consequently, GdCu2 nanoparticles display a dual disorder-driven magnetic dynamics, which are the one ascribed to the magnetically frustrated moments located at the nanoparticle surface; and that of uncompensated antiferromagnetic moments located within the nanoparticle core.
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| 5. |
- Posth, Oliver, et al.
(författare)
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Classification of analysis methods for characterization of magnetic nanoparticle properties
- 2015
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Ingår i: 21st IMEKO World Congress 2015. - 9781510812925 ; , s. 1310-1315
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Konferensbidrag (refereegranskat)abstract
- The aim of this paper is to provide a roadmap for the standardization of magnetic nanoparticle (MNP) characterization. We have assessed common MNP analysis techniques under various criteria in order to define the methods that can be used as either standard techniques for magnetic particle characterization or those that can be used to obtain a comprehensive picture of a MNP system. This classification is the first step on the way to develop standards for nanoparticle characterization.
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