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| 2. |
- Mulders, A. M., et al.
(författare)
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On The Interface Magnetism Of Thin Oxidized Co Films : Orbital And Spin Moments
- 2009
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 21:12, s. 124211-
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Tidskriftsartikel (refereegranskat)abstract
- An x-ray magnetic circular dichroism study of a polycrystalline Co/CoO bilayer is presented. Using both the chemical specificity and surface sensitivity in the core level techniques, we find that uncompensated Co2+ spin moments participate in the remanent ferromagnetic response of the bilayer that has oxygen nearest neighbors. These are likely located at the Co/CoO interface. As intermixing of magnetic species is not present in Co/CoO, it is concluded that the observed interface moments are due to interface roughness. Given their direction, these moments appear to not directly correlate to the exchange bias in these bilayers.
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| 3. |
- Karlsson, Krister
(författare)
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Self-consistent GW combined with single-site dynamical mean field theory for a Hubbard model
- 2005
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 17:48, s. 7573-7598
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Tidskriftsartikel (refereegranskat)abstract
- We combine the single-site dynamical mean field theory (DMFT) with the non-local GW method. This is done fully self-consistently and we apply our formalism to a one-band Hubbard model. Eventually at self-consistency the full self-energy and polarization operator of the system are retrieved. Some numerical results, in the metallic as well as the insulator regime, are presented and briefly discussed. Depending on the involved interaction (GW) parameters, substantial changes are found when the GW self-energy is incorporated. However, the main point of this work is to demonstrate the applicability of the method, not to make any strict comparison with exact results and experiments.
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| 4. |
- Manchon, A., et al.
(författare)
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Currents and torques due to spin-dependent diffraction in ferromagnetic/spin spiral bilayers
- 2008
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Ingår i: Journal of Physics. - : Institute of Physics (IOP). - 0953-8984 .- 1361-648X. ; 20:50, s. 505213-
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Tidskriftsartikel (refereegranskat)abstract
- Spin-dependent transport through the interface between a ferromagnet and a spin spiral is investigated using both ballistic and diffusive models. We find that spin-dependent interferences lead to a new type of diffraction called 'spin diffraction'. It is shown that this spin diffraction leads to local spin and electrical current along the interface, as well as spin transfer torque acting on the spin spiral. This study also emphasizes that in highly inhomogeneous magnetic configurations, diffracted electrons must be taken into account to properly describe the spin transport.
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| 5. |
- Björström, Cecilia M., et al.
(författare)
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Multilayer formation in spin-coated thin films of low-bandgap polyfluorene:PCBM blends
- 2005
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Ingår i: Journal of Physics. - Philadelphia : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 17:50, s. L529-L534
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Tidskriftsartikel (refereegranskat)abstract
- Blends of the low-bandgap polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5- (4',7'-di-2-thienyl-2',1',3'-benzothiadiazole] (APFO-3) and the fullerene derivative [6,6]-phenyl–C61–butyric acid methyl ester (PCBM) were spin-coated from chloroform solution into thin films, which were examined with dynamic secondary ion mass spectrometry. For blends with high PCBM content, the depth profiles show composition waves that were caused by surface-directed phase separation during spin-coating. The formation of such multilayer structures by spontaneous self-stratification is likely to have implications for optimization strategies for the performance of organic solar cells
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| 6. |
- Ahlström, Bodil, 1968, et al.
(författare)
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Prediction of structures and gel transitions in systems of colloids with moderate-range attractions
- 2007
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Ingår i: Journal of Physics. Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 19, s. 036102-036117
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Tidskriftsartikel (refereegranskat)abstract
- Predictions of glass transitions from the idealized mode-coupling theory (MCT) are tested for systems with intermediate-range particle attractions. Liquid structure input to MCT is provided by the Asakura–Oosawa (AO) theory for the depletion interaction, used as an idealized model for structures in colloid–polymer mixtures. The effective one-component formulation of the AO theory is verified to capture the complete pair structure found from the binary version of the theory also for polymer–colloid size ratios somewhat larger than those for which an exact mapping of the two descriptions holds. The Percus–Yevick theory is shown to provide an accurate structural input to MCT, at least in the single-phase fluid region. With this combination of theories, very reasonable predictions for locations of glassy states in the experimental phase diagram are obtained for polymer–colloid size ratios somewhat larger than have been considered before. Simple approximations are also suggested for extracting the remaining pair structure from calculations of the one-component AO theory.
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| 7. |
- Bolinsson, J, et al.
(författare)
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Direct observation of atomic scale surface relaxation in ortho twin structures in GaAs by XSTM
- 2009
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Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 1361-648X .- 0953-8984. ; 21:5
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the (110) GaAs surface of a structure containing ortho twins by cross-sectional scanning tunnelling microscopy and we have compared the experimental results with ab initio density functional theory calculations and STM simulations. Both experimentally and theoretically we find that the surface of different twin crystallites are significantly displaced with respect to each other, parallel to the twin boundary. This result is explained by a surface relaxation of the atoms in the (110) GaAs surface and the difference between the atomic configuration of the ortho twins.
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| 8. |
- Ellström, Carl, et al.
(författare)
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Exciton fine structure splitting in InP quantum dots in GaInP
- 2007
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Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 1361-648X .- 0953-8984. ; 19:29
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the electronic structure of excitons in InP quantum dots in GaInP. The exciton is theoretically expected to have four states. Two of the states are allowed to optically decay to the ground ( vacuum) state in the dipole approximation. We see these two lines in photoluminescence (PL) experiments and find that the splitting between the lines ( the fine structure splitting) is 150(+/- 30) mu eV. The lines were perpendicularly polarized. We verified that the lines arise from neutral excitons by using correlation spectroscopy. The theoretical calculations show that the polarization of the emission lines are along and perpendicular to the major axis of elongated dots. The fine structure splitting depends on the degree of elongation of the dots and is close to zero for dots of cylindrical symmetry, despite the influence of the piezoelectric polarization, which is included in the calculation.
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| 9. |
- Engström, Christian
(författare)
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Structural information of nanocomposites from measured optical properties
- 2007
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Ingår i: Journal of Physics. - : Institute of Physics (IOP). - 0953-8984 .- 1361-648X. ; 19:10
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Tidskriftsartikel (refereegranskat)abstract
- This paper is concerned with the estimation of the volume fraction and the anisotropy of a two-component composite from measured bulk properties. An algorithm that takes into account that measurements have errors is developed. This algorithm is used to study data from experimental measurements for a nanocomposite with an unknown nanostructure. The dependence on the nanostructure is quantified in terms of a measure in the representation formula introduced by D Bergman. We use composites with known nanostructures to illustrate the dependence on the underlying measure and show how errors in the measurements affect the estimates of the structural parameters.
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| 10. |
- Irbäck, Anders
(författare)
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Peptide folding and aggregation studied using a simplified atomic model
- 2005
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Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 1361-648X .- 0953-8984. ; 17:18, s. 1553-1564
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Tidskriftsartikel (refereegranskat)abstract
- Using an atomic model with a simplified-sequence-based potential, the folding properties of several different peptides are studied. Both alpha-helical (Trp cage, F-s) and beta-sheet(GB1p, GB1m2, GB1m3, Betanova, LLM) peptides are considered. The model is able to fold these different peptides for one and the same choice of;parameters, and the melting behaviour of the peptides (folded population against temperature) is in very good agreement with experimental data. Furthermore, using the same model with unchanged parameters, the aggregation behaviour of a fibril-forming fragment of the Alzheimer's A beta peptide is studied, with very promising results.
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