| 1. |
- Ambrazaitis, Gilbert, 1979-, et al.
(författare)
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Auditory vs. audiovisual prominence ratings of speech involving spontaneously produced head movements
- 2022
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Ingår i: Proceedings of the 11th International Conference on Speech Prosody : Speech Prosody 2022 - Speech Prosody 2022. - : International Speech Communication Association. - 2333-2042. ; , s. 352-356, s. 352-356
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Konferensbidrag (refereegranskat)abstract
- Visual information can be integrated in prominence perception, but most available evidence stems from controlled experimental settings, often involving synthetic stimuli. The present study provides evidence from spontaneously produced head gestures that occurred in Swedish television news readings. Sixteen short clips (containing 218 words in total) were rated for word prominence by 85 adult volunteers in a between-subjects design (44 in an audio-visual vs. 41 in an audio-only condition) using a web-based rating task. As an initial test of overall rating behavior, average prominence across all 218 words was compared between the two conditions, revealing no significant difference. In a second step, we compared normalized prominence ratings between the two conditions for all 218 words individually. These results displayed significant (or near significant, p
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| 2. |
- Bergman, Anders, et al.
(författare)
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A first-principles study of the magnetism and electronic structure of Cr clusters supported on a Au(111) surface
- 2007
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 19:15, s. 156226-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied clusters of Cr on a Au(111) surface by means of a first-principles method that allows for non-collinear magnetic ordering. We find that the Cr atoms possess a large magnetic moment, of order 4 μB/atom, and have essentially antiferromagnetic interatomic exchange interactions. This leads to collinear magnetic arrangements in linear clusters (dimers and trimers) and non-collinear ordering in clusters where antiferromagnetism becomes frustrated, such as in triangular geometries.
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| 3. |
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| 4. |
- Bergman, Anders, et al.
(författare)
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Magnetic interactions of Mn clusters supported on Cu
- 2006
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Ingår i: PHYSICAL REVIEW B. - 1098-0121. ; 73:17, s. 174434-
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Tidskriftsartikel (refereegranskat)abstract
- It is demonstrated that the magnetic interactions can be drastically different for nanosized systems compared to those of bulk or surfaces. Using a real-space formalism we have developed a method to calculate noncollinear magnetization structures and hence exchange interactions. Our results for magnetic Mn clusters supported on a Cu(111) surface show that the magnetic ordering as a rule is noncollinear and cannot always be described by using a simple Heisenberg Hamiltonian. We argue that the use of ab initio calculations allowing for noncollinear coupling between atomic spins constitutes an efficient and reliable way of analyzing nanosized magnets.
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| 5. |
- Bergman, Anders, et al.
(författare)
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Magnetic properties of Fe/Co(001) superlattices from first-principles theory
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 74:17
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of Fe/Co(001) superlattices have been studied using fully-relativistic first-principles theories. The average magnetic moment shows a behavior similar to bulk Fe-Co alloys, i.e., an enhanced magnetic moment for low Co concentrations, as described by the Slater-Pauling curve. The maximum of the magnetization curve, however, is lowered and shifted towards the Fe-rich compositions. The increased average magnetic moment for the Fe-rich superlattices, compared to bulk Fe, is due to an enhancement of the Fe spin moment close to the Fe-Co interface. The orbital moments were found to be of the same size as in bulk. The effect of interface roughness on the magnetic properties was investigated, and it was found that-despite local fluctuations due to the varying coordination-the average magnetic moment is only slightly affected. From a mapping of first-principles interactions onto the screened generalized perturbation method, we calculate the temperatures for when Fe/Co superlattices break up into an alloy configuration. Furthermore, the tetragonal distortion of the superlattice structure was found to only have a minor effect on the magnetic moments. Also, the calculated easy axis of magnetization is in the film plane for all compositions studied. It lies along the [100] direction for Fe-rich superlattices and along the [110] direction for Co-rich compositions. The transition of the easy axis occurs around a Co concentration of 50%.
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| 6. |
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| 7. |
- Bergman, Anders, et al.
(författare)
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Magnetic structures of small Fe, Mn, and Cr clusters supported on Cu(111) : Noncollinear first-principles calculations
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:22, s. 224425-
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic structures of small clusters of Fe, Mn, and Cr supported on a Cu(111) surface have been studied with noncollinear first-principles theory. Different geometries such as triangles, pyramids, and wires are considered and the cluster sizes have been varied between two and ten atoms. The calculations have been performed using a real-space linear muffin-tin orbital method. The Fe clusters are found to order ferromagnetically regardless of the cluster geometry. For Mn and Cr clusters, antiferromagnetic exchange interactions between nearest neighbors are found to cause collinear antiferromagnetic ordering when the geometry allows it. If the antiferromagnetism is frustrated by the cluster geometry, noncollinear ordering is found. A comparison between the calculated structures and ground states obtained from simplified Heisenberg Hamiltonians show that the exchange interaction varies for different atoms in the clusters as a result of the different local structure.
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| 8. |
- Bergman, Anders, et al.
(författare)
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Magnetism of Co overlayers and nanostructures on W(001) : A first principles study
- 2008
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 320:6, s. 1173-1179
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of Co nanostructures and a Co monolayer on W(001) have been studied in the framework of density functional theory. Different geometries such as planar and three-dimensional clusters have been considered, with cluster sizes varying between 2 and 13 atoms. The calculations were performed using the real-space linear muffin-tin orbital method (RS-LMTO-ASA). With respect to the stability of the magnetic state, we predict an antiferromagnetic (AFM) structure for the ground state of the planar Co clusters and a ferromagnetic (FM) state for the three-dimensional clusters. For the three-dimensional clusters, one of the AFM arrangements leads to frustration due to the competing FM and AFM exchange interactions between different atoms in the cluster, and gives rise to a non-collinear state with energy close to that of the FM ground state. The relative role of the Co-Co and Co-W exchange interactions is also investigated.
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| 9. |
- Bergman, Anders, et al.
(författare)
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Magnetism of Fe clusters embedded in a Co matrix from first-principles theory
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:17, s. 174446-
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Tidskriftsartikel (refereegranskat)abstract
- We have calculated spin and orbital moments for Fe clusters of sizes up to 700 atoms embedded as impurities in a bcc Co matrix. The calculations have been carried out using relativistic first-principles real-space density functional theory, and we have made a comparison with earlier experimental studies. For Fe atoms close to theFeCo interface, the spin moments are found to increase while atoms far from the interface exhibit bulklike moments. The Co moments remain essentially unchanged and close to the moment of bulk bcc Co. With increasing cluster size, the average moments of the cluster atoms decrease due to the decreased surface to volume ratio. The orbital moments of both Fe and Co are calculated to be small and they stay almost constant regardless of cluster size. Our results for spin moments agree with experimental data but the calculated orbital moments are slightly underestimated. A simplified model indicates that a compound of close-packed Fe clusters surrounded by Co show higher average total moments compared to bulk and multilayer systems with a similar concentration. This increase seems to disappear when cluster-cluster interactions are taken into account. The general trend is that for a given alloy concentration of FexCo1−x, clustering tends to lower the average magnetic moment compared to that of ordered structures and random alloys.
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| 10. |
- Bergman, Anders, et al.
(författare)
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Non-collinear magnetisation of V clusters supported on a Cu (111) surface : Theory
- 2006
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 600:21, s. 4838-4842
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic properties and electronic structure of V clusters supported on a Cu (111) substrate, have been calculated from a first principles method. We observe in general non-collinear magnetic structures that are the result of antiferromagnetic interactions on a frustrated lattice. The values of the magnetic moments range from similar to 0 to 2.7 mu(B)/atom, depending on cluster geometry.
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