| 1. |
- Nyholm, R., et al.
(författare)
-
ELECTRONIC AND STRUCTURAL-PROPERTIES OF THE CU-BI2CASR2CU2O8 INTERFACE
- 1991
-
Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 180:1-4, s. 120-123
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of the Cu-Bi2CaSr2Cu2O8 interface has been studied by photoelectron spectroscopy using synchrotron radiation. Photon energies in the range 20-1000 eV were utilized in order to probe both the valence band and to monitor chemical changes upon Cu deposition, as revealed by the core-level shifts. A strong chemical reaction between Bi2CaSr2CuO8 and Cu is manifested by the formation of metallic Bi. From the intensity variations as a function of electron emission angle it is shown that the metallic Bi segregates to the top surface layer.
|
|
| 2. |
- Nyholm, R., et al.
(författare)
-
PHOTOEMISSION-STUDY OF THE BI2CASR2CU2O8 SUPERCONDUCTOR WITH CU, AG AND AU OVERLAYERS
- 1993
-
Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 218:1-2, s. 103-108
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a photoemission study of the interaction of Cu, Ag and Au with clean single-crystal Bi2CaSr2Cu2O8 superconductor surfaces. Both the valence-band and the Bi 5d, O 1 s and Sr 3d core levels were monitored for all overlayers. Cu, Ag and Au were deposited as consecutively thicker layers starting with a third of a monolayer and progressing in steps up to a deposition in the range of eight monolayers. Comparing the results for the different overlayers reveals the Ag overlayer to be less reactive than Au which causes the formation of metallic Bi on cleaved Bi2CaSr2Cu2O8 surface. Cu is shown to be the most reactive of the three metals. The Au and Ag overlayers display an island-growth mode, while Cu grows in a layer-by-layer fashion.
|
|
| 3. |
- Ambrosch-Draxl, C., et al.
(författare)
-
First-principles study of oxygen ordering in YBa2Cu3O7-x
- 2000
-
Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 341, s. 1997-1998
-
Tidskriftsartikel (refereegranskat)abstract
- We have performed first-principles calculations considering different patterns of oxygen/vacancy ordering in the Cu-O chains of YBa2Cu3O7-x. From the total-energy values we determine the effective interactions of the oxygen atoms within the basal plane by using the cluster expansion technique. Furthermore, we discuss the effect of ordering to the density of states at the Fermi level.
|
|
| 4. |
- Andersson, Britt M., et al.
(författare)
-
Electrical transport properties of dense bulk YBa2Cu4O8 produced by hot isostatic pressing
- 1990
-
Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 170:5-6, s. 521-531
-
Tidskriftsartikel (refereegranskat)abstract
- Highly dense sintered YBa2Cu4O8 has been produced by hot isostatic pressing (HIP). The electrical resistivity varrho of this material has been measured as a function of temperature T and pressure varrho in the range 40–650 K and 0–0.7 GPa. Both the temperature dependence and the pressure dependence of varrho are found to be well described by a model based on the standard Bloch-Grüneisen theory. It is pointed out that varrho is liner in T only under isobaric conditions, while varrho is strongly nonlinear in all high-Tc superconductors under isochoric (constant volume) conditions. The critical current density of the material is 900 A/cm2 at 4 K, while the resistivity is 630 μΩ cm at 294 K.
|
|
| 5. |
- Andersson, Britt M., et al.
(författare)
-
Thermal conductivity of YBa2Cu4O8 under high pressure
- 1993
-
Ingår i: Physica. C, Superconductivity. - : Elsevier B.V.. - 0921-4534 .- 1873-2143. ; 216:1-2, s. 187-194
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal diffusivity a of YBa2Cu4O8 (1-2-4) has been measured as a function of pressure p and temperature T over the range 85
|
|
| 6. |
- Andersson, Magnus, et al.
(författare)
-
H-T PHASE-DIAGRAM OF DYBA2CU3O7-DELTA(Y0.45PR0.55)BA2CU3O7-DELTA MULTILAYERS IN THE MIXED-STATE
- 1994
-
Ingår i: Physica. C, Superconductivity. - : Elsevier BV. - 0921-4534 .- 1873-2143. ; 235, s. 2617-2618
-
Tidskriftsartikel (refereegranskat)abstract
- From measurements of I-V characteristics of DyBa2Cu3O7-delta/(Y0.45Pr0.55)Ba2Cu3O7.delta multilayers, we have experimentally determined the characteristic temperature separating the vortex liquid from the vortex solid. We suggest that the cross-over temperature is determined by the anisotropy given by the artificially layered structure of these multilayers and that the studied system can be used as a test system for vortex dynamics.
|
|
| 7. |
- Andersson, Magnus, et al.
(författare)
-
MAGNETORESISTANCE MEASUREMENTS ON (CA,TH)-DOPED YBA2CU3O7-DELTA
- 1991
-
Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 185, s. 1901-1902
-
Tidskriftsartikel (refereegranskat)abstract
- Magnetoresistance measurements on sintered Y1-2xCaxThxBa2Cu3O7-delta samples with x < = 0.1 are reported. By fitting the measured data to the Hikami-Larkin theory, we obtain coherence lengths, xi-ab and xi-c’ and a phase breaking time tau-phi All these parameters are found to decrease with (Ca,Th) doping. We also conclude that magnetoresistance measurements are highly sensitive to inhomogeneities in the sample.
|
|
| 8. |
- Andersson, Magnus, et al.
(författare)
-
Neutron-diffraction studies of Ca-Pr doped YBa2Cu307-delta
- 1993
-
Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 205:1-2, s. 105-110
-
Tidskriftsartikel (refereegranskat)abstract
- We have performed neutron powder diffraction on samples in a series Y1-2xCaxPrxBa2Cu3O7-delta, with x=0.0, 0.1 and 0.2, and analyzed the data with the Rietveld refinement method. Small changes were observed in atomic bond distances when the amount of Ca-Pr was increased. In general, these changes could qualitatively be viewed as the sum of effects from the Ca and Pr substitutions in YBa2Cu3O7-delta samples. Analyses of the distance between the superconducting CuO2 Planes suggest that the Pr ions in the Ca-Pr substituted samples have an effective valence close to + 4.
|
|
| 9. |
- Andersson, Magnus, et al.
(författare)
-
NEUTRON-DIFFRACTION STUDIES OF Y1-2XCAXTHXBA2CU3O7-DELTA WITH X-LESS-THAN=0.1
- 1991
-
Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 185, s. 915-916
-
Tidskriftsartikel (refereegranskat)abstract
- We have made Rietveld refinements on neutron powder diffraction data from Y1-2xCaxThxBa2Cu3O7-delta samples with x < = 0.1. Only small changes in lattice distances are detected. Most noticeable are a flattening of the CuO-planes and a possible small increase in the distance between Cu(1) and the edge oxygen O(4). A comparison with the Y1-xCaxBa2Cu3O7-delta system is made.
|
|
| 10. |
- Andersson, Magnus, et al.
(författare)
-
STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF Y1-2XCAXPRXBA2CU3O7-GAMMA
- 1992
-
Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 190:3, s. 255-260
-
Tidskriftsartikel (refereegranskat)abstract
- Samples of the nominal composition Y1-2xCaxPrxBa2Cu3O7-delta with 0 less-than-or-equal-to x less-than-or-equal-to 0.4 have been studied by X-ray diffraction techniques, chemical analyses, and measurements of the super conducting transition temperature and the upper critical magnetic field. For x less-than-or-equal-to 0.25, the results indicate that Ca and Pr can both replace Y in agreement with the nominal composition, while for x > 0.25 only Pr enters the orthorhombic unit cell. Compared to Pr substitution in 1:2:3 we observe small changes in the depression of T(c) and strong changes in the critical field slopes. These results suggest that if Pr has a magnetic pair-breaking effect, it is close to being temperature independent.
|
|
