| 1. |
- Ndiaye, W., et al.
(författare)
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Bulk electronic structure of Mn5Ge3/Ge(111) films by angle-resolved photoemission spectroscopy
- 2013
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 87:16
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Tidskriftsartikel (refereegranskat)abstract
- Mn5Ge3(001) thin films grown on Ge(111)-c(2 x 8) reconstructed surfaces were studied by angle-resolved photoemission using synchrotron radiation in the 14-94 eV photon energy range. The results obtained in the Gamma ALM plane and in the Gamma AHK plane are in agreement with simulations starting with band structure calculations based on the density functional theory. This provides a unique validation of band structure calculations for a proper description of the electronic properties of Mn5Ge3. Only the spectral feature very close to the Fermi level cannot be well explained by the simulation. This departure is discussed in terms of the three-dimensional nature of the sample and of correlation effects.
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| 2. |
- Ndiaye, W., et al.
(författare)
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k dependence of the spin polarization in Mn5Ge3/Ge(111) thin films
- 2015
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 91:12
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Tidskriftsartikel (refereegranskat)abstract
- Mn5Ge3(001) thin films grown on Ge(111) were studied by angle-and spin-resolved photoemission using synchrotron radiation in the 17-40 eV photon energy range. The photoelectron spectra were simulated starting from a first-principles band-structure calculation for the ground state, using the free-electron approximation for the final states, taking into account photohole lifetime effects and k(perpendicular to) broadening plus correlation effects, but ignoring transition matrix elements. The measured spin polarizations for the various k points investigated in the Gamma MLA plane of the Brillouin zone are found to be in fair enough agreement with the simulated ones, providing a strong support to the ground-state band-structure calculations. Possible origins for the departures between either simulations and experiments or previous and present experiments are discussed.
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| 3. |
- Hellsvik, J., et al.
(författare)
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Tuning order-by-disorder multiferroicity in CuO by doping
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 90:1, s. 014437-
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Tidskriftsartikel (refereegranskat)abstract
- The high Curie temperature multiferroic compound CuO has a quasidegenerate magnetic ground state that makes it prone to manipulation by the so-called "order-by-disorder" mechanism. First principle computations supplemented with Monte Carlo simulations and experiments show that isovalent doping allows us to stabilize the multiferroic phase in nonferroelectric regions of the pristine material phase diagram with experiments reaching a 250% widening of the ferroelectric temperature window with 5% of Zn doping. Our results allow us to validate the importance of a quasidegenerate ground state on promoting multiferroicity on CuO at high temperatures and open a path to the material engineering of multiferroic materials. In addition we present a complete explanation of the CuO phase diagram and a computation on the incommensurability in excellent agreement with experiment without free parameters.
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| 4. |
- Stroppa, A., et al.
(författare)
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Adsorption and Dissociation of CO on Bare and Ni-Decorated Stepped Rh(553) Surfaces
- 2009
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:3, s. 942-949
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption and dissociation of carbon monoxide were studied with plane-wave density functional theory on flat Rh(111), stepped and kinked Rh(553), and Ni-decorated Rh(553) surfaces. The theoretical results were compared to high-resolution X-ray photoelectron spectroscopy (HR-XPS) experiments. The most favorable CO adsorption sites for low coverages were identified by a systematic calculation of the adsorption energies, and their sequence of occupation as a function of CO exposure was determined experimentally in C 1s HR-XPS spectra via their characteristic surface core-level shifts. On the clean, stepped (553) surface, molecular CO is adsorbed more strongly on low-coordinated top sites at the step edge, but on the Ni-decorated surface, the binding is stronger at the terrace sites. The barrier for dissociation with respect to the gas phase is about 1 eV lower on the stepped Rh(553) surface than on the flat Rh(111) surface, implying a substantially higher reaction rate. The presence of kinks at the clean Rh(553) surface does not lead to a significant additional decrease of the dissociation barriers, resulting in dissociation energies just above the desorption threshold for both stepped and kinked surfaces, whereas the barrier can be additionally lowered by about 0.1 eV by decorating the step edges with Ni stripes. Whereas no dissociation of CO was observed by HR-XPS on the clean Rh(553) surface, a minor amount of CO dissociation was found on the Ni-decorated Rh surface, in agreement with the theoretical predictions.
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