The anisotropy of the irreversible magnetizations of YBCO and LaSrCuO: Evidence for a transition from Abrikosov to Josephson vortices in LaSrCuO
✍ Scribed by S. Senoussi; F. Mosbah; O. Sarrhini; S. Hammond
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- English
- Weight
- 775 KB
- Volume
- 211
- Category
- Article
- ISSN
- 0921-4534
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✦ Synopsis
The anisotropy of the magnetization and the critical current density of the high temperature superconductors YBa2Cu3OT_6 and La~.a~Sro.tsCuO4 are investigated as a function of the orientation 0 of the applied field with respect to the crystallographic caxis. The results are analyzed in the framework of the recent model by Bulaevskii et al. In agreement with this model, there is a threshold angle 0o( ~ 50 ° ) beyond which the vortex line lattice enters the sample parallel to the ab planes and then undergoes a lock-unlock transition at a field tti of the order of llc~.c/cos O. In addition, at high fields the vortex lattice of Lat.ssSro.~sCuO4 exhibits a sharp change in a narrow angle of less than one degree around the ab basal planes. No anomalous behavior of this kind is seen in YBa2Cu307_6. In this angular domain the critical current density of La Ls~Sr0.~CuO, increases slightly with temperature while that of YBa2Cu3OT_6 drops sharply in the same reduced temperature range. These data are hard to interpret with existing pinning theories and are tentatively ascribed to a gradual transformation from Josephson-like to Abrikosov-like vortices in the LaSr based compound which is much more anisotropic than YBCO material.