| 1. |
- Avdoshenko, S. M., et al.
(författare)
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Partial magnetic ordering in one-dimensional arrays of endofullerene single-molecule magnet peapods
- 2018
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Ingår i: Nanoscale. - 2040-3372. ; , s. 18153-18160
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic ordering and bistability of one-dimensional chains of endofullerene Dy2ScN@C80 single-molecule magnets (SMMs) packed inside single-walled carbon nanotubes (SWCNTs) have been studied using high-resolution transmission electron microscopy (HRTEM), X-ray magnetic circular dichroism (XMCD), and ab initio calculations. X-ray absorption measurements reveal that the orientation of the encapsulated endofullerenes differs from the isotropic distribution in the bulk sample, indicating a partial ordering of the endofullerenes inside the SWCNTs. The effect of the one-dimensional packing was further investigated by ab initio calculations, demonstrating that for specific tube diameters, the encapsulation is leading to energetically preferential orientations of the endohedral clusters. Additionally, element-specific magnetization curves reveal a decreased magnetic bistability of the encapsulated Dy2ScN@C80 SMMs compared to the bulk analog.
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| 2. |
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| 3. |
- Blomberg, Sara, et al.
(författare)
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A high pressure X-ray photoelectron spectroscopy study of oxidation and reduction of Rh(100) and Rh nanoparticles
- 2014
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 628, s. 153-158
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the oxidation and reduction of Rh(100) and SiO2 supported Rh particles using high pressure X-ray photoelectron spectroscopy. We show that the formation and reduction of Rh bulk oxide can be followed in situ in O-2 and CO pressures in the range of 0.1 Torr. In general, the oxidation/reduction processes are similar on Rh(100) and the nanoparticles, but there are significant differences in temperature dependence. Already at a sample temperature of 140 degrees C, the particles show clear signs of a thin bulk oxide, while an ultra-thin so-called surface oxide covers the single crystal at the same temperature. Both of these oxide films, however, hinder further oxidation, and a thick oxide is only found at a temperature of at least 300 degrees C, for both samples. The reduction, in contrast, starts at a higher temperature on the particles as compared to the single crystal, but once started the particles are completely reduced at lower temperatures. (C) 2014 Elsevier B.V. All rights reserved.
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| 4. |
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| 5. |
- Blomberg, Sara, et al.
(författare)
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Structure of the Rh2O3(0001) surface
- 2012
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 606:17-18, s. 1416-1421
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the (0001) surface termination of Rh2O3 on a Rh(111) single crystal using a combination of high resolution core level spectroscopy, low energy electron diffraction, scanning tunneling microscopy and density functional theory. By exposing the Rh(111) to atomic oxygen we are able to grow Rh2O3 layers exposing the (0001) surface. The experiments support the theoretical predictions stating that the surface is terminated with an O-Rh-O trilayer yielding a RhO2 termination instead of a bulk Rh2O3 termination. The structural details as found by the DFT calculations are presented and reasons for the previously observed strong differences in catalytic activity between the structurally similar RhO2 surface oxide, and the Rh2O3(0001) surface are discussed. (C) 2012 Elsevier B.V. All rights reserved.
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| 6. |
- Bulbucan, Claudiu, et al.
(författare)
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Cr-substituted Fe3O4 nanoparticles : The role of particle size in the formation of FexO sub-domains and the emergence of exchange bias
- 2023
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853. ; 570
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Tidskriftsartikel (refereegranskat)abstract
- Here we study the influence of particle size on the formation of antiferromagnetic FexO subdomains and the emergence of exchange bias in novel ferrimagnetic Cr-substituted Fe3O4 nanoparticles generated using an aerosol technique based on spark ablation. Cooling in an applied magnetic field across the Néel temperature of the FexO subdomains results in significant shifts in the hysteresis loops, which decrease in magnitude with the particle diameter for the two large systems (D≈20nm&D≈40nm), whereas only minor exchange fields are observed for the smallest system (D≈10nm). The reduced exchange bias is attributed to the metastable FexO's lower volume fraction and size due to a facile transformation into the thermodynamically stable (Fe,Cr)3O4 phase with decreasing particle diameter.
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| 7. |
- Bulbucan, Claudiu, et al.
(författare)
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Large exchange bias in Cr substituted Fe3O4nanoparticles with FeO subdomains
- 2021
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 13:37, s. 15844-15852
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Tidskriftsartikel (refereegranskat)abstract
- Tuning the anisotropy through exchange bias in bimagnetic nanoparticles is an active research strategy for enhancing and tailoring the magnetic properties for a wide range of applications. Here we present a structural and magnetic characterization of unique FeCr-oxide nanoparticles generated from seed material with a Fe : Cr ratio of 4.71 : 1 using a physical aerosol method based on spark ablation. The nanoparticles have a novel bimagnetic structure composed of a 40 nm ferrimagnetic Cr-substituted Fe3O4 structure with 4 nm antiferromagnetic FexO subdomains. Cooling in an applied magnetic field across the Néel temperature of the FexO subdomains results in a significant shift in the hysteresis, demonstrating the presence of a large exchange bias. The observed shift of μ0HE = 460 mT is among the largest values reported for FexO-Fe3O4-based nanoparticles and is attributed to the large antiferromagnetic-ferrimagnetic interface area provided by the subdomains.
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| 8. |
- Cavar, Elizabeta, et al.
(författare)
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A single h-BN layer on Pt(111)
- 2008
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 602:9, s. 1722-1726
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Tidskriftsartikel (refereegranskat)abstract
- The structure and formation of an ultrathin hexagonal boron nitride (h-BN) film on Pt(111) has been studied by a combination of scanning tunneling microscopy, low energy electron diffraction, low energy electron microscopy, X-ray absorption and high resolution core level spectroscopy. The study shows that a single boron nitride layer is formed on Pt(111), resulting in a coincidence structure. High resolution scanning tunneling microscopy (STM) images of the h-BN ultrathin film display only one of the atomic species in the unit cell. Probing the boron and nitrogen related local density of states by near edge X-ray absorption fine structure measurements we conclude that the nitrogen sublattice is visible in STM images. The growth of the single hexagonal boron nitride layer by vapourized borazine in the pressure range of 1 x 10(-6)-1 x 10(-8) at 800 degrees C is further studied by low energy electron microscopy, and reveals that the number of nucleation sites and the perfection of the growth is strongly pressure dependent. A model for the single, hexagonal, boron nitride layer on Pt(111) is proposed.
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| 9. |
- Deppert, Knut, et al.
(författare)
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Magnetic-field directed self-assembly and chain formation of functional aerosol nanoparticles
- 2020
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Konferensbidrag (refereegranskat)abstract
- Self-assembly of nanoparticles into vertical structures or larger ensembles can be a powerful method to achieve a strong collective behavior while still obtaining many of the same properties of the individual nanoparticles. In this study, we achieve directed self-assembly of magnetic nanoparticles into nanochains when depositing in a combined magnetic and electric field (M-ESP). We show that the Co nanoparticles are spontaneously magnetized in the aerosol phase, and that the role of the external magnetic field is mainly to guide the deposition in a certain direction.Lastly, we will present chain formation of mixed materials. Here, we combine a strong magnetic material, with other elements to achieve the same chain structure, but with a desired surface functionalization. Nanoparticle chains can therefore be formed with different functionalities, depending on the mixing material. This opens up for further combination to tune the functionalization of the nanoparticle chain structure.
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| 10. |
- Dreiser, Jan, et al.
(författare)
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The Metallofullerene Field-Induced Single-Ion Magnet HoSc2N@C-80
- 2014
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 20:42, s. 13536-13540
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Tidskriftsartikel (refereegranskat)abstract
- The low-temperature magnetic properties of the endohedral metallofullerene HoSc2N@C-80 have been studied by superconducting quantum interference device (SQUID) magnetometry. Alternating current (ac) susceptibility measurements reveal that this molecule exhibits slow relaxation of magnetization in a small applied field with timescales in the order of milliseconds. The equilibrium magnetic properties of HoSc2N@C-80 indicate strong magnetic anisotropy. The large differences in magnetization relaxation times between the present compound and the previously investigated DySc2N@C-80 are discussed.
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