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- 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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| 4. |
- Karis, O., et al.
(författare)
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Observation of short- and long-range hybridization of a buried Cu monolayer in Ni
- 2000
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 62:24, s. R16239-R16242
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of a Cu monolayer buried in Ni fcc(100) is studied by means of x-ray emission and absorption spectroscopies in combination with first principles calculations. The local character of the x-ray probes allows us to investigate changes in the chemical interaction for these ultrathin film systems. In comparison to bulk Cu, the occupied d states of a buried Cu monolayer, as mapped in the x-ray emission spectrum, remain mostly unaltered. The absorption spectrum on the other hand shows that the empty states of the buried Cu monolayer are modified, and instead resemble the unoccupied electronic density of bulk Ni. These findings agree well with our first principle electronic structure calculations and the results are interpreted in terms of short- and long-range hybridization.
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| 5. |
- Karis, O, et al.
(författare)
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Probing surface states of Cu/Ni thin films using x-ray absorption spectroscopy
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 63:11
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Tidskriftsartikel (refereegranskat)abstract
- Surface and interface properties of Cu thin films (1–4 monolayers) deposited on Ni(100) have been extracted by means of x-ray absorption spectroscopy and analyzed in combination with ab initio density-functional calculations. An unoccupied Cu surface state is identified in an x-ray absorption spectra and studied as a function of film thickness. Experimental data is supported by calculations of the layer-resolved density of states and the results from this combined theoretical-experimental effort show that the surface state is almost entirely located on the atomic layer closest to the vacuum. Our results also indicate strong hybridization between unoccupied states at the Cu/Ni interface boundary.
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| 9. |
- Olovsson, W., et al.
(författare)
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Relationship between the electronic structure of embedded single to triple atomic monolayers and bulk alloys
- 2005
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 72:15, s. 5419-
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Tidskriftsartikel (refereegranskat)abstract
- The relation between the electronic structure of thin film nanosandwiches and bulk alloys has been investigated by means of first-principles electronic structure theory. The spin magnetization, layered projected spectral properties, and interface core-level shifts of Cu, Ni, Co, and Fe systems have been calculated. In order to compare thin films to bulk alloys, systems with equal average nearest-neighbor coordination have been compared. We find that the spin magnetization and interface core level shifts are closely related to bulk with the exception of the core level shifts in the Fe/Cu multilayers, which are more sensitive to the specific structure of the thin film geometry. The discrepancy is discussed in terms of interacting interface states in the Cu spacer. The experimental possibility of detecting embedded monolayers is also investigated. © 2005 The American Physical Society.
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