Experimental evidence of twin-planes pinning in the ab plane studied in large c-axis YBa2Cu3O7 samples

摘要

The twin-planes (TP) effect on pinning is studied in large monodomain YBa2Cu3O7 textured samples with the size along the c axis greater than the others. The magnetic field angular dependence of the c-asis resistivity and c-axis critical current density has been carried out using transport and dc-magnetization measurements. These various experimental methods show clearly that in this configuration TP's dominate the pinning properties in the ab planes at high temperatures (T greater than or equal to 40 K) and when the magnetic field is close to the TP directions. Moreover, experiments demonstrate that the TP's enhance the ab-plane irreversibility line for angles close to a critical angle Phi(c)similar to 8 degrees-10 degrees. The observed properties are related to the extended and correlated character of the twin planes. An experimental phase diagram for the angular dependence of the ab-plane irreversibility line is proposed with a possible existence of a Bose glass phase in the ab plane induced by the two directions of the TP's. The persistence of the TP pinning for magnetic fields higher than 20 T is explained with an electromagnetic origin induced by the surface character of TP's. [S0163-1829(98)08241-1]. [References: 57]