| 1. |
- Kravtsov, E, et al.
(författare)
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Fine-tuning of the spin-density-wave state in Cr/V heterostructures via hydrogen uptake
- 2009
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 21:33, s. 336004-
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Tidskriftsartikel (refereegranskat)abstract
- We show that the magnetic state in rather thick Cr films can be finely tuned via hydrogen uptake into adjacent vanadium layers at rather low hydrogen pressures. By changing the hydrogen concentration and, hence, the electronic structure in the V layers, it is possible to affect the global properties of spin-density waves (SDWs) in Cr layers, including the SDW period and the Neel temperature. We provide direct experimental evidence that hydrogen uptake into V layers can be used to switch between incommensurate and commensurate SDW states in a reproducible way.
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| 2. |
- Kravtsov, Evgeny, et al.
(författare)
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Onset of spin-density-wave antiferromagnetism in Cr/V multilayers
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:2, s. 024421-
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Tidskriftsartikel (refereegranskat)abstract
- Spin-density-wave (SDW) magnetism in a series of Cr/V heterostructures with different Cr thicknesses was systematically investigated by combined resistivity, neutron, and synchrotron scattering measurements. We show that the onset of the bulklike SDW state comes through several necessary steps from a paramagnetic state through a commensurate SDW to an incommensurate SDW. The Néel temperature for the incommensurate SDW is found to scale with Cr thickness and reaches the bulk value at a Cr thickness of about 2000 Å. The proximity effect from Cr/V interfaces is found to lead to (i) the appearance of a 50-Å magnetically dead Cr layer near Cr/V interfaces and (ii) suppression of the spin-flip transition and stabilization of a single-domain SDW with out-of-plane spins and out-of-plane propagation wave vector. Finally, we show that the SDW period increases with decreasing Cr thickness and becomes temperature independent in sufficiently thin Cr layers.
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| 3. |
- Maldonado, Pablo, et al.
(författare)
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Crystal dynamics and thermal properties of neptunium dioxide
- 2016
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Ingår i: PHYSICAL REVIEW B. - 2469-9950. ; 93:14
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Tidskriftsartikel (refereegranskat)abstract
- We report an experimental and theoretical investigation of the lattice dynamics and thermal properties of the actinide dioxide NpO2. The energy-wave-vector dispersion relation for normal modes of vibration propagating along the [001], [110], and [111] high-symmetry lines in NpO2 at room temperature has been determined by measuring the coherent one-phonon scattering of x rays from an similar to 1.2-mg single-crystal specimen, the largest available single crystal for this compound. The results are compared against ab initio phonon dispersions computed within the first-principles density functional theory in the generalized gradient approximation plus Hubbard U correlation (GGA+U) approach, taking into account third-order anharmonicity effects in the quasiharmonic approximation. Good agreement with the experiment is obtained for calculations with an on-site Coulomb parameter U = 4 eV and Hund's exchange J = 0.6 eV in line with previous electronic structure calculations. We further compute the thermal expansion, heat capacity, thermal conductivity, phonon linewidth, and thermal phonon softening, and compare with available experiments. The theoretical and measured heat capacities are in close agreement with another. About 27% of the calculated thermal conductivity is due to phonons with energy higher than 25 meV (similar to 6 THz), suggesting an important role of high-energy optical phonons in the heat transport. The simulated thermal expansion reproduces well the experimental data up to about 1000 K, indicating a failure of the quasiharmonic approximation above this limit.
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| 4. |
- Panaccione, G., et al.
(författare)
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Coherent peaks and minimal probing depth in photoemission spectroscopy of Mott-Hubbard systems
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:11
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Tidskriftsartikel (refereegranskat)abstract
- We have measured hard x-ray photoemission spectra of pure vanadium sesquioxide (V2O3) across its metal-insulator transition. We show that, in the metallic phase, a clear correlation exists between the shakedown satellites observed in the vanadium 2p and 3p core-level spectra and the coherent peak measured at the Fermi level. Comparing experimental results and dynamical mean-field theory calculations, we estimate the Hubbard energy U in V2O3 (4.20 +/- 0.05 eV). From our bulk-sensitive photoemission spectra we infer the existence of a critical probing depth for investigating electronic properties in strongly correlated solids.
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