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| 5. |
- Arvanitis, Dimitri, et al.
(författare)
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Influence of ligand states on the relationship between orbital moment and magnetocrystalline anisotropy
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:17, s. 177207-
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Tidskriftsartikel (refereegranskat)abstract
- The spin and orbital moments of Au/Co/Au trilayers grown on a W(110) single crystal substrate have been investigated by means of x-ray magnetic circular dichroism. Our findings suggest that the orbital moment of Co does not obtain a maximum value along the easy axis, in contrast with previous experience. This is attributed to the large spin-orbit interaction within the Au caps. Both second order perturbation theory and first principles calculations show how the magnetocrystalline anisotropy (MCA) is dramatically influenced by this effect, and how this leads to the fact that the orbital moment anisotropy is not proportional to the MCA.
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| 6. |
- Escala-Garcia, Maria, et al.
(författare)
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A network analysis to identify mediators of germline-driven differences in breast cancer prognosis
- 2020
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Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Identifying the underlying genetic drivers of the heritability of breast cancer prognosis remains elusive. We adapt a network-based approach to handle underpowered complex datasets to provide new insights into the potential function of germline variants in breast cancer prognosis. This network-based analysis studies similar to 7.3 million variants in 84,457 breast cancer patients in relation to breast cancer survival and confirms the results on 12,381 independent patients. Aggregating the prognostic effects of genetic variants across multiple genes, we identify four gene modules associated with survival in estrogen receptor (ER)-negative and one in ER-positive disease. The modules show biological enrichment for cancer-related processes such as G-alpha signaling, circadian clock, angiogenesis, and Rho-GTPases in apoptosis.
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- Hahlin, Anders, et al.
(författare)
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Structure and magnetism on in-situ ultrathin epitaxial films : XMCD and EXAFS on Fe/Ag(100)
- 2003
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Ingår i: Proceedings of the 7th International Conference on Nanometer-Scale Science and Technology and the 21st European Conference on Surface Science. ; , s. 76-81
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Konferensbidrag (refereegranskat)abstract
- We have made in situ investigations of epitaxial ultrathin Fe films on Ag(1 0 0). This system is known to exhibit a reorientation of the magnetization, dependent of Fe thickness and temperature. Our aim here is to correlate the local structure with the magnetic properties of this system. The X-ray absorption fine structure has been recorded in situ both in the near edge as well as in the extended X-ray absorption fine structure (EXAFS) range. Using X-ray magnetic circular dichroism we find that, below 300 K, films between 2 and 6 monolayers show an out-of-plane remanent magnetization whereas for thicker films the magnetization lies in-plane. By making use of the Fe L-edge EXAFS we obtain information on the local structure around the Fe atoms, such as the interatomic distances, the coordination number, and the mean square relative displacement of the first neighbor shells.
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| 11. |
- Hahlin, A, et al.
(författare)
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Ultrathin Co films on flat and stepped Cu(111) surfaces: Determination of per atom orbital and spin moments
- 2002
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Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 91:10, s. 6881-6883
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Tidskriftsartikel (refereegranskat)abstract
- We have used the x-ray magnetic circular dichroism technique to characterize ultrathin Co films deposited on flat and vicinal Cu(111) single crystal surfaces. All films were prepared and characterized in situ, in ultrahigh vacuum. Similar to other investigators we report a 40% increase of the ratio m(l)/m(s) (orbital to spin moment) of ultrathin Co on both flat and vicinal Cu(111). In addition, an apparently correlated enhancement of both the orbital and spin moments is observed for Co on vicinal Cu(111). This finding is in contrast to what has earlier been reported for a similar system, Co on vicinal Cu(100). (C) 2002 American Institute of Physics.
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- Hahlin, A, et al.
(författare)
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Ultrathin Co films on flat and vicinal Cu(111) surfaces: per atom determination of orbital and spin moments
- 2003
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Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 0953-8984. ; 15:5, s. 573-586
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Konferensbidrag (refereegranskat)abstract
- We have performed x-ray magnetic circular dichroism, x-ray resonant magnetic scattering and scanning tunnelling microscopy measurements on ultrathin Co films deposited on flat and vicinal Cu(111). The range of film thickness varies between one and 25 monolayers. For the vicinal Cu(111), Co deposition below one monolayer leads to the formation of elongated islands preferentially oriented along the step edges. These islands extend over lateral length scales of up to several thousand angstroms. For the thicker films we still observe that the vicinal surface leads to the occurrence of a preferential uniaxial growth direction. No such preferential growth direction can be identified for the flat surface. In correlation to the Co growth we observe an increase of both the orbital and the spin moment per Co atom on vicinal Cu(111) of about 25% versus what was observed for Co on flat Cu(111). This enhancement is observed in both the x-ray absorption and the reflectivity measurements. Similar to what was earlier reported for Co on Cu(100) we also observe for the case Co on Cu(111) an increase in the ratio m(l)/m(s), (orbital to spin moments) of 40% for thin Co films. In contrast to what has been reported for Co films on flat and vicinal Cu(100) we do not observe any major variations in the occupancy of the Co 3d states for Co grown on the vicinal Cu(111) surface.
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- Hunter Dunn, Jonathan, et al.
(författare)
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Elliptically polarised soft X-rays produced using a local bump in MAX II characterisation of the degree of polarisation
- 2004
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 705, s. 65-68
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Konferensbidrag (refereegranskat)abstract
- MAX-lab has introduced a local perturbation to the electron orbit of the MAX II storage ring, providing users at the SX700 monochromator beam line, D1011, with elliptically polarised soft X-rays. This is achieved by using corrector magnets to send the electron orbit on an ascending or descending trajectory through the dipole magnet source. This simple "bump" approach has many advantages over and above insertion device based solutions. To illustrate the potential of the approach, the degree of circular polarisation, Pc, has both been calculated and measured. The calculation was made by applying the Stokes formalism to the intensities given by the standard dipole emission formula. Experimentally Pc was characterised using X-ray magnetic circular dichroism measurements. In such experiments magnetic contrast scales directly proportional to Pc. Using a 25 atomic layer bcc Fe film deposited on the Cu(100) surface as a calibration standard the spin moment, ms, was determined. By comparing the values of ms obtained here with those reported earlier, the degree of circular polarisation could be estimated. At ~715 eV the calculated and measured values of Pc are 0.93 and 0.85, respectively
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| 16. |
- Hunter Dunn, Jonathan, et al.
(författare)
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Vanishing Magnetic Interactions in Ferromagnetic Thin Films
- 2005
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Ingår i: PHYSICAL REVIEW LETTERS. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 94:21, s. 217202-
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Tidskriftsartikel (refereegranskat)abstract
- We have used element-specific hysteresis measurements, based on the x-ray magnetic circular dichroism technique, to investigate magnetic trilayer structures composed of Fe and Ni layers. Within a critical regime we have discovered a class of structures in which the exchange interaction, the mechanism responsible for the macroscopic magnetism, can become vanishingly small. The experimental observations are supported by first principles theory and are explained as arising from a cancellation of several competing magnetic interactions. Hence, we have discovered a system with a novel exchange interaction between magnetic layers in direct contact that replaces the conventional exchange interaction in ferromagnets.
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| 17. |
- Hunter Dunn, Jonathan
(författare)
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Very thin magnets : X-rays, lasers and spectroscopy
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The magnetic properties of transition metal films are investigated using synchrotron based x-ray absorption and x-ray photoelectron spectroscopy. These techniques are elementally selective and may therefore be used, either to probe a specific element in a multicomponent system or, as very sensitive magnetometers. These are complemented by magneto-optic measurements using laser light. Based on x-ray absorption spectroscopy, a new technique for the accurate measurement of critical properties ofthin films is presented. In the present work the emphasis has been on high quality, ultra thin thin films prepared and measured in ultra high vacuum. These films have been stabilised in different crystallographic structures than those normally found for bulk samples by deposition on the (100) surface of copper.The systematic study of these films has facilitated the observation of novel phenomena related to their unique character. The orbital moment of the surface layer is enhanced. Such effects are supported by theory. Energy shifts in x-ray absorption features are quantified and linked to the magnetic character of the spectra.In an attempt to better understand the absorption spectrum, of thin films, a series of Ni films were oxidised. These data are interpreted in terms of the charge transfer between the Ni and O in the resulting oxide which is correlated with the redistribution of intensity in the resulting absorption spectra.Using x-ray photoelectron spectroscop the Fe/Cu(100) system was investigated. Magnetic contrast was discovered for an experimental geometry where such effects are forbidden from symmetry considerations. In combination with theory, we address the reorientation of the remnant magnetisation for this system upon the addition of sub monolayers of cobalt. Adding magnetic contrast to L edge extended x-ray absorption fine structure measurements of 3d ferromagnets, highlights the subtle interplay between magnetism and local crystal structure via the spin polarisation dependence of the scattered electron wave.Evidence is presented that demonstrates how the degree of spatial coherence of the x-ray source effects the relative intensity of spectral features in x-ray absorption spectroscopy.
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| 21. |
- Pierce, MS, et al.
(författare)
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Disorder-induced microscopic magnetic memory
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 94:1
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Tidskriftsartikel (refereegranskat)abstract
- Using coherent x-ray speckle metrology, we have measured the influence of disorder on major loop return point memory (RPM) and complementary point memory (CPM) for a series of perpendicular anisotropy Co/Pt multilayer films. In the low disorder limit, the domain structures show no memory with field cycling-no RPM and no CPM. With increasing disorder, we observe the onset and the saturation of both the RPM and the CPM. These results provide the first direct ensemble-sensitive experimental study of the effects of varying disorder on microscopic magnetic memory and are compared against the predictions of existing theories.
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| 22. |
- Removic-Langer, K, et al.
(författare)
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Spin and orbital moments in Au/Co/Au(111)/W(110) across the spin-reorientation transition-temperature
- 2003
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 200, s. 210-214
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Tidskriftsartikel (refereegranskat)abstract
- The temperature-driven spin-reorientation transition (SRT) has been investigated in a layer of 2.1 nm Co in Au/Co/Au. We studied the evolution and stability of the in-plane magnetization components in the temperature range from 300 to 90 K by means of polarized neutron reflectometry (PNR) and Co L-edge X-ray magnetic circular dichroism (XMCD) measurements. The PNR measurement provides evidence for the occurrence of a SRT in this temperature range. XMCD can be used as a vector magnetometer that yields both the in- and out-of-plane magnetization components per Co atom. Combining the results of both techniques (PNR and XMCD) allows separating the orbital and spin magnetic moments using magneto-optical sum rules. We observed that already above the SRT the in-plane orbital moment component changes significantly stronger than the spin component. (C) 2002 Elsevier Science B.V. All rights reserved.
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