| 1. |
- Butorin, S.M, et al.
(författare)
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Tunable excitation x-ray-fluorescence spectroscopy in phase-analysis of high-Tc superconductors
- 1994
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Ingår i: Journal of physics-condensed matter. - 0953-8984. ; 6:43, s. 9267-9274
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Tidskriftsartikel (refereegranskat)abstract
- O Kalpha x-ray fluorescence of YBa2Cu3O7-delta and Sr0.85Nd0.15CuO2 samples containing CO3(2-) impurities, as well as pure BaCO3, have been studied using tunable monochromatic synchrotron radiation excitation. When the excitation energy is set to the most intense features in the O 1s absorption edge of cuprates and to bound states above this edge the O Kalpha spectra recorded are very similar to those of pure BaCO3 even if the admixture of CO3(2-) is small. The observed changes in the O Kalpha profiles of multi-phase YBa2Cu3O7-delta and Sr0.85Nd0.15CuO2 samples are discussed in terms of different x-ray absorption cross sections for O in the main phase and in the CO3(2-) fraction.
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| 2. |
- Yang, Z.J., et al.
(författare)
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Study of flux motion in Bi-based superconductors by a pendulum
- 1992
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Ingår i: Journal of Superconductivity. - 0896-1107 .- 1572-9605. ; 5:2, s. 127-135
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Tidskriftsartikel (refereegranskat)abstract
- Using a computerized mechanical pendulum, we have studied the lateral magnetic flux motion of the Bi-based high-T c superconductors in the quasi-static magnetic field (0.1 Hz) for the range 1 μm to 0.35 mm. The effect of d.c. and a.c. transport currents on the flux motion has also been investigated. We argue that the lateral magnetic stiffness is a measure of the pinning potential of the fluxoids in the superconductors. The pinning energy barrier ε is estimated to be about 0.3 eV based on the stiffness measurements, which is comparable with the data from the YBa2Cu3O7-χ superconductors.
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| 3. |
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| 4. |
- Johansen, T.H., et al.
(författare)
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Transition from elastic to dissipative motion in a magnet-high-Tc superconductor system
- 1991
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 70:12, s. 7496-7499
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Tidskriftsartikel (refereegranskat)abstract
- Using quasistatic harmonic excitations, we have measured the lateral force between a permanent magnet and a Bi-based ceramic high-Tc superconductor (HTSC) for lateral displacement amplitudes down to 1 µm. We find clear evidence for a transition from elastic (nondissipative) to inelastic interaction, and attribute the effect to flux pinning. The crossover amplitude can easily reach several micrometers, with the consequence that the lateral disturbance of a levitated magnet will decay to this amplitude, whereas further damping will be extremely slow. For applications of HTSCs in magnetic bearing systems this can be a very relevant aspect of the interaction, and it can set the limit for precision positioning of levitated objects
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| 5. |
- Wassdahl, N., et al.
(författare)
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Soft x-ray emission studies of adsorbates
- 1992
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Ingår i: Physical Review Letters. - 0031-9007. ; 69:5, s. 812-815
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Tidskriftsartikel (refereegranskat)abstract
- Soft x-ray emission spectroscopy is for the first time applied to surfaces and adsorbates. Surface sensitivity is achieved by employing synchrotron radiation in grazing incidence for the excitation. We present O K emission from adsorbed atomic oxygen on Ni(100) and Cu(100) and molecular CO on Ni(100). The observed spectral features correspond to the occupied 2p partial density of states of the adsorbates.
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