| 1. |
- ANDERSEN, JN, et al.
(författare)
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SURFACE CORE-LEVEL SHIFTS OF INAS(110)
- 1990
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 41:6, s. 3844-3846
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Andersson, Britt M., et al.
(författare)
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Thermal conductivity of polycrystalline YBa2Cu4O8
- 1994
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 49:6, s. 4189-4198
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the thermal conductivity κ and the thermal diffusivity a of a dense bulk ceramic polycrystalline sample of YBa2Cu4O8 (1:2:4) in the temperature range 30–300 K. We find κ≊10 W m-1 K-1 at 100 K, significantly higher than in ceramic YBa2Cu3O7-δ (1:2:3) and approaching the in-plane value for single-crystal 1:2:3, and decreasing to 7.6 W m-1 K-1 at 300 K. The data for this sample can be described by standard theories for phonon thermal conductivity of crystalline materials with boundary, phonon, and electron scattering. The higher κ in 1:2:4 as compared to 1:2:3 is, in this model, due to the smaller point defect scattering in the former. The fitted parameters for the three scattering mechanisms all agree with independent estimates based on simple models; inserting data for electric resistivity, grain size, carrier density, and lattice properties we can predict κ and its T dependence to within about 20%. We also discuss models for the phonon and electron thermal conductivities in some detail, including some second-order effects such as inelastic electron scattering and a T-dependent carrier density.
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| 3. |
- ANDERSSON, CBM, et al.
(författare)
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SURFACE ELECTRONIC-STRUCTURE OF INAS(110)
- 1993
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 47:4, s. 2427-2430
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the InAs(I 10) cleavage surface has been studied by angle-resolved photoelectron spectroscopy. The bulk band structure has been calculated utilizing the augmented plane-wave method and then the bulk bands have been projected along the lines GAMMA-XBARBAR and GAMMA-YBARBAR of the surface Brillouin zone (SBZ). Three surface-related structures have been found and their initial state versus k parallel-to dispersion along the line GAMMA-XBARBAR and the line GAMMA-YBARBAR of the SBZ has been determined. The structures are identified as A5, A4, and A3 along GAMMA-XBARBAR and as A5, A4, and C2 along GAMMA-YBARBAR.
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| 4. |
- ANDERSSON, JO, et al.
(författare)
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OVERLAP LENGTH IN A CU-MN SPIN-GLASS PROBED BY AC SUSCEPTIBILITY
- 1993
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 48, s. 13977-13980
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Tidskriftsartikel (refereegranskat)abstract
- An important theoretical concept in the ‘’droplet” model of spin glasses is the existence of an overlap length. Experimentally this concept was verified by dc-magnetization measurements. However, recent ac-susceptibility measurements by Lefloch et al. [Europhys. Lett. 18, 647 (1992)] have been interpreted to contradict this result. In this paper, ac-susceptibility and dc-magnetization measurements on a Cu (2% Mn) spin glass are reported. The results of the ac-susceptibility measurements are consistent with dc measurements and provide evidence for the existence of an overlap length in 3d spin glasses at low temperatures.
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| 5. |
- Andersson, Magnus, et al.
(författare)
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CA AND PR SUBSTITUTION IN Y-BASED AND SM-BASED 1-2-3 COMPOUNDS
- 1993
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 48:10, s. 7590-7597
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Tidskriftsartikel (refereegranskat)abstract
- Substitution with equal amounts of Ca and Pr has been studied mainly in Y- and Sm-based 1:2:3 samples and with some results also for Nd-based samples. Structural and chemical analysis and measurements of the superconducting T(c) and the upper critical magnetic field were performed. It was found that Ca and Pr can be dissolved in the orthorhombic structure up to about 25 at. % each in both Y- and Sm-based samples while for larger concentrations, only Pr continued to enter into the 1:2:3 structure. The depression of T(c) with Ca-Pr doping was found to be linear in concentration in contrast to the accelerated decrease in samples doped with only Pr. The rate of depression of T(c) increased in the sequence Y-, Sm-, and Nd-based hosts. The results suggest that Ca-Pr doping isolates a characteristic Pr-impurity effect in 1:2:3 samples. The critical magnetic-field slopes of Y- and Sm-based samples were almost independent of Ca-Pr content in the cosolubility region while a strong decrease was observed for larger Pr content, similar to 1:2:3 samples doped with Pr only. These results suggest an almost-temperature-independent magnetic pair-breaking effect by Pr.
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| 6. |
- Andersson, Magnus, et al.
(författare)
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MAGNETORESISTANCE MEASUREMENTS ON POLYCRYSTALLINE YBA2CU3O7-DELTA
- 1991
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 44:14, s. 7722-7725
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Tidskriftsartikel (refereegranskat)abstract
- The magnetoresistance of a polycrystalline sample of YBa2Cu3O7-delta has been measured by an ordinary resistive method at temperatures from about 1 to 15 K above T(c) and in magnetic fields up to 12 T. From our experimental results and the theory of Hikami and Larkin, we obtain values of the coherence lengths xi-ab = 15.6 angstrom and xi-c = 3.6 angstrom and of the phase-breaking time tau-phi = 1.8 x 10(-13) s.
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| 7. |
- Andersson, Magnus, et al.
(författare)
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RELATION BETWEEN THE CU(1)-O(4) DISTANCE AND T(C) IN Y1-2XCAXTHXBA2CU3O7-DELTA - RAMAN-SCATTERING AND CALCULATION OF THE ELECTRON-PHONON INTERACTION
- 1992
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 46:10, s. 6501-6504
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Tidskriftsartikel (refereegranskat)abstract
- The strong depression of T(c) with Ca-Th substitution in Y1-2xCaxThxBa2Cu3O7-delta has been investigated in a model calculation of the electronic and phononic contributions from the apex oxygen, O(4), on the electron-phonon interaction, lambda. The shift with Ca-Th substitution of the characteristic O(4) vibrational mode was measured by Raman scattering. The electronic part eta of lambda has been calculated at several distances between chain Cu(1) and O(4) in the region of the observed variation with x. Eta was found to depend strongly on this distance. The results show a small increase with x of the O(4) frequency and a strong decrease of eta. Both these factors thus contribute to a decrease of lambda. We therefore find evidence that a decreasing electron-phonon interaction is associated with the depression of T(c) in Ca-Th substituted YBa2Cu3O7-delta.
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| 8. |
- Andersson, Ove, et al.
(författare)
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Thermal conductivity of the Ih and XI phases of ice
- 1994
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 50:10, s. 6583-6588
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity λ of KOH-doped ice was measured using the transient hot-wire method at temperatures in the range 55–250 K and at pressures up to 0.15 GPa. With an isobaric increase of temperature at 0.08 GPa, λ decreased 17% at about 74 K. This decrease is associated with the known transition from ordered phase XI to phase Ih which exhibits orientational disorder of H2O. A model for λ indicates that the decrease of λ at the transition is due to an increase of the lattice anharmonicity which might be caused by the disorder in phase Ih. It was inferred from the temperature dependence of λ that phonon scattering in both phases Ih and XI is dominated by three phonon umklapp processes. At 58 K, λ of supercooled phase Ih decreased slightly with increasing pressure whereas λ of phase XI was independent of pressure.
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| 9. |
- Chauhan, H. S., et al.
(författare)
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Direct- and inverse-photoemission investigations of the electronic structure of Cd(0001)
- 1993
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 48:7, s. 4729-4734
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Tidskriftsartikel (refereegranskat)abstract
- Photoemission and inverse angle-resolved photoemission spectra are presented for Cd(0001). The data are interpreted in terms of interband transitions, density-of-states effects, and excitations of surface states.
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| 10. |
- Chen, W., et al.
(författare)
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Electronic and geometric structure of clean Pt3Ti(111)
- 1994
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Ingår i: Physical Review B. - 0163-1829 .- 1095-3795. ; 50:8, s. 5620-5627
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Tidskriftsartikel (refereegranskat)abstract
- Photoemission spectra and scanning tunneling microscopy (STM) images of the clean Pt3Ti(111) surface are presented. Grazing-emission core-level spectra show that the topmost layer is pure platinum, modified compared with the Pt(111) surface. The Pt 4f levels at the surface are shifted 0.4 eV toward the Fermi level relative to bulk Pt3Ti while the Pt 4f and Ti 2p levels in the bulk are shifted 0.4 and 1.3 eV to higher binding energy relative to pure bulk platinum and titanium, respectively, Tunneling measurements show a surface with only metallic atoms and a small p(2×2) buckling. Our observations of molecularly adsorbed CO are not compatible with metallic titanium atoms at the surface and the STM data thus indirectly confirm that only platinum atoms are present in the topmost layer. Linear muffin-tin-orbital calculations of the bulk band structure and valence-band photoemission spectra reveal highly hybridized electron states between the Pt d and Ti d levels. The calculations give a minor charge transfer from Ti to Pt, 0.37 electrons per Ti atom, but the large core-level shifts reflect the stability of the alloy and the response to the excitation rather than the amount of charge transfer. The observed segregation of platinum to the surface and the altered electronic structure of the topmost layer, due to interaction with the underlying alloy, are in full agreement with earlier conclusions based on low-energy electron-diffraction measurements and on the chemical properties of the surface. © 1994 The American Physical Society.
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