HIGH-FIELD MAGNETIZATION OF SINGLE-CRYSTALLINE YBA2CU3O7

Magnetization measurements have been performed on samples composed of oriented YBa2Cu3O7 single crystals 1.4 K, 68 K and 78 K in magnetic fields up to 38 T applied along the c-axis and within the ab-plane. The critical currents are deduced from the irreversible magnetization and discussed in terms of pinning forces. At low temperature (1.4 K), the experimental data with the field along the c-axis are compared with a theoretical model for the field dependence of the pinning force. At higher temperatures (68 K and 78 K), the pinning force can be described by a Kramer-like scaling law: Fp=A[B0(T)]mbp(1-b)q, where B0 is the field where the irreversibility of the magnetization disappears and where b(=B/B0) is the reduced field. For the exponent m, the usual value of 2.5 is found; approximate values for p and q are around 2 and 4, respectively. © 1990.