Formation of the magnetization loops of high‐Tc superconductors

Abstract

AbstractWe have investigated the irreversibility magnetic field and the critical current density of the high temperature superconductor YBa2Cu3O7–δ single crystal. Vibrating sample magnetometer (V.S.M.) method was used for these measurements. Magnetization hysteresis loops scale and shape are strongly dependent on the temperature values and the angle θ between the direction of the applied magnetic field and c‐axis. For the large single crystals at very low temperature the loops present several flux jumps “saw‐tooth” and we observe the second peak “fish‐tail” for high temperature values but not with applied magnetic field perpendicular to the ab ‐planes. Beyond θ = 30°, the irreversibility field Hirr increases deviates from different temperature values. The variation of the critical current density Jc with applied magnetic field parallel to c‐axis for different temperatures was studied. Here, Jc is an effective critical current density deduced from the measured magnetization by the Bean formula. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)