| 1. |
- Lopez-Ortega, Alberto, et al.
(författare)
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Size-Dependent Passivation Shell and Magnetic Properties in Antiferromagnetic/Ferrimagnetic Core/Shell MnO Nanoparticles
- 2010
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 132:27, s. 9398-9407
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of bimagnetic core/shell nanoparticles consisting of an antiferromagnetic MnO core and a ferrimagnetic passivation shell have been investigated. It is found that the phase of the passivation shell (gamma-Mn2O3 or Mn3O4) depends on the size of the nanoparticles. Structural and magnetic characterizations concur that while the smallest nanoparticles have a predominantly gamma-Mn2O3 shell, larger ones have increasing amounts of Mn3O4. A considerable enhancement of the Neel temperature, T-N, and the magnetic anisotropy of the MnO core for decreasing core sizes has been observed. The size reduction also leads to other phenomena such as persistent magnetic moment in MnO up to high temperatures and an unusual temperature behavior of the magnetic domains.
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| 2. |
- Pistidda, Claudio, et al.
(författare)
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Synthesis of amorphous Mg(BH4)(2) from MgB2 and H-2 at room temperature
- 2010
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 508:1, s. 212-215
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Tidskriftsartikel (refereegranskat)abstract
- Due to its high hydrogen content and its favourable overall thermodynamics magnesium tetrahydroborate has been considered interesting for hydrogen storage applications. In this work we show that unsolvated amorphous magnesium tetrahydroborate can be obtained by reactive ball milling of commercial MgB2 under 100 bar hydrogen atmosphere. The material was characterized by solid-state NMR which showed the characteristic features of Mg(BH4)(2), together with those of higher borohydride species. High pressure DSC and TPD-MS showed thermal behaviour similar to that of Mg(BH4)(2) but with broadened signals. In situ synchrotron X-ray powder diffraction confirmed the amorphous state of the material and showed the typical crystalline decomposition products of Mg(BH4)(2) at elevated temperatures. (C) 2010 Elsevier B.V. All rights reserved.
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| 3. |
- Salazar-Alvarez, German, et al.
(författare)
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Reversible post-synthesis tuning of the superparamagnetic blocking temperature of gamma-Fe2O3 nanoparticles by adsorption and desorption of Co(II) ions
- 2007
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 17:4, s. 322-328
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the post-synthesis adsorption of Co(II) ions on the structural and magnetic properties of maghemite (gamma-Fe2O3) nanoparticles with a mean particle size of about 10 nm has been investigated. It is shown that the step-wise adsorption of Co( II) can controllably increase the blocking temperature, T-B, of the system up to 60 K with respect to that of untreated particles, while neither the particle size nor the particle size distribution are significantly modified. This is accompanied by a four-fold increase in the coercivity, H-C, at low temperatures. Using a selective leaching of the previously adsorbed Co(II) ions the T-B and H-C values of the pristine gamma-Fe2O3 nanoparticles are recovered. Hence, a reversible and controllable tailoring of the magnetic properties (e.g., T-B and H-C) of the gamma-Fe2O3 nanoparticles can be achieved by a simple adsorption and desorption process of Co( II) ions after their synthesis.
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| 4. |
- Salazar-Alvarez, German, et al.
(författare)
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Two-, Three-, and Four-Component Magnetic Multilayer Onion Nanoparticles Based on Iron Oxides and Manganese Oxides
- 2011
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 133:42, s. 16738-16741
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic multilayered, onion-like, hetero-structured nanoparticles are interesting model systems for studying magnetic exchange coupling phenomena. In this work, we synthesized heterostructured magnetic nanopartides composed of two, three, or four components using iron oxide seeds for the subsequent deposition of manganese oxide. The MnO layer was allowed either to passivate fully in air to form an outer layer of Mn(3)O(4) or to oxidize partially to form MnO vertical bar Mn(3)O(4) double layers. Through control of the degree of passivation of the seeds, particles with up to four different magnetic layers can be obtained (i.e., FeO vertical bar Fe(3)O(4)vertical bar MnO vertical bar Mn(3)O(4)). Magnetic characterization of the samples confirmed the presence of the different magnetic layers.
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