Geometric barrier in Bi2Sr2CaCu2O7+δ single crystals

In this paper we present isothermal magnetization curves measured by using a Bi 2 Sr 2 CaCu 2 O 7 + Φ single crystal in the temperature range 50 K-80 K, for external magnetic fields applied along the sample thickness. The experimental data is compared with the numerically calculated magnetization, in which the specimen geometry is correctly taken into account. In this calculation an explicit equilibrium relation H = H(B,κ) is also considered, where K is related to the Ginzburg-Landau parameter. The reversible experimental and calculated magnetizations show good agreement, allowing us to estimate H c 1 (T). The results show that the geometric harrier is mainly responsible for the magnetic hysteresis observed at high temperatures (T≥70 K) where hulk pinning is negligible.