| Автор | S K Misra |
| Автор | L E Misiak |
| Дата выпуска | 1989-11-27 |
| dc.description | X- and Q-band electron paramagnetic resonance studies have been carried out on a polycrystalline superconductor YBa<sub>1.9</sub>Na<sub>0.1</sub>Cu<sub>3</sub>O<sub>7- delta </sub> (Y-Ba-Na-Cu-O) over the temperature range 4.2-300 K. It is concluded that the monovalent Na<sup>+</sup> ions substitute for Ba<sup>2+</sup> ions, and not for Cu<sup>2+</sup> ions. The onset of the superconducting transition is determined to occur at 91 K, while the absorption of microwaves in low magnetic fields begins to occur below 100 K. The value of the upper critical field estimated here, as well as that of the specific heat coefficient are lower than those reported for the pure YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7- delta </sub> ceramic. The local symmetry about the Cu<sup>2+</sup> ion in the phase of the sample with increased oxygen vacancy content, responsible for the Cu<sup>2+</sup> EPR signal, is deduced to be orthorhombic over the entire range of temperature investigated, as revealed by the Cu<sup>2+</sup> principal values (g<sub>z</sub>, g<sub>x</sub> and g<sub>y</sub>), which are, in turn, used to estimate the energy-level sequence for the Cu<sup>2+</sup> ion. The covalency effect due to Cu-O bonding is found to be significant. The hyperfined splitting constant mod A<sub>z</sub> mod , as estimated from the weak hyperfine structure at low magnetic fields, is estimated to be 8 mT at 4.2 K. The sample exhibits magnetic memory in the superconducting state. |
| Формат | application.pdf |
| Издатель | Institute of Physics Publishing |
| Название | An EPR investigation of the high-T<sub>c</sub> superconductor YBa<sub>1.9</sub>Na<sub>0.1</sub>Cu<sub>3</sub>O<sub>7-δ</sub> |
| Тип | paper |
| DOI | 10.1088/0953-8984/1/47/018 |
| Electronic ISSN | 1361-648X |
| Print ISSN | 0953-8984 |
| Журнал | Journal of Physics: Condensed Matter |
| Том | 1 |
| Первая страница | 9499 |
| Последняя страница | 9508 |
| Аффилиация | S K Misra; Dept. of Phys., Concordia Univ., Montreal, Que., Canada |
| Аффилиация | L E Misiak; Dept. of Phys., Concordia Univ., Montreal, Que., Canada |
| Выпуск | 47 |
