Field and temperature dependence of the anisotropy ratio in a high-Tc superconductor
Laboratoire de magnétisme Louis Néel, CNRS, B.P. 166,
38042 Grenoble Cedex 9, France
2 Laboratoire de chimie minérale B, Université de Rennes 1, CNRS, 35042 Rennes Cedex, France
Accepted: 13 May 1996
Using a double SQUID magnetometer, the angular dependence of the transverse (MT) and longitudinal (ML) components of the magnetization vector have been measured simultaneously on a () and on a () single crystal. The reversible and irreversible contributions of each component of the magnetization can be separated. The angular variations of the ratio of the reversible components have been analysed with the 3D anisotropic Ginzburg-Landau theory. The derived anisotropy factor γ is found to depend on the applied field. In , this behaviour is attributed to field-induced reduction of the proximity effect of non-superconducting layers. In quasi-2D , this interpretation is not relevant and our data show rather the lock-in transition of the vortex lines.
PACS: 74.50.+r – Proximity effects, weak links, tunneling phenomena, and Josephson effects / 75.30.Gw – Magnetic anisotropy / 74.60.Ec – Mixed state, critical fields, and surface sheath
© EDP Sciences, 1996