Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10557225 | Microchemical Journal | 2005 | 10 Pages |
Abstract
The onset of electro-magnetic optic effects, observed at the Ba L2,3 edges synchrotron X-ray absorption by a YBa2Cu3O7 single crystal, 20 K above the transition temperature to superconductivity, Tc â¼Â 92 K is used to identify the role played by the Ba donor layer in the transition to superconductivity in the CuO2 layers. Negative permeability leads to Faraday rotation of the transmitted beam below T = 112 to 56 K for the 22 μm thick single crystal (c-axis orientation of 8Ï/18 relative to εX-rays) and sharp changes in the density of empty final states lead to zero transmitted radiation in an interval ÎE at the given orientation. The temperature dependence: ÎE(L2) = 1.4, 3.5 and 3.9 eV, while ÎE(L3) = 5.3, 6 and 7 eV at T = 92, 74 and 63 K, respectively, indicates that the width of the empty final states bands increases as T decreases. ÎE(L3)/ÎE(L2) = 3.8 at 92 K to 1.8 at 63 K also indicates that the d5/2 symmetry bands fill faster than those of d3/2 symmetry below Tc, providing the first experimental evidence of unpaired spin-orbit states in the Ba donor layer of a superconductor. These effects, characteristic of ferromagnetic and anti-ferromagnetic materials near a resonance absorption, signal the onset of a Mott transition. The interaction between the layer states is described using 1D conjugate molecular orbitals.
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
J.V. Acrivos,