TEMPERATURE-DEPENDENCE, WITH IMPLICATION OF VORTEX GLASS BEHAVIOR, OF REMANENT MAGNETIZATION IN Y-BA-CU-O POWDERS AND CERAMICS

Temperature dependence of the thermoremanent magnetization (M(R)(T)) has been investigated in YBa2Cu3O7-delta powders and ceramics after cooling the sample in a magnetic field. When the density of vortices in the grains is high, M(R)(T) can be expressed with an exponential law by using an effective activation energy U(eff) related to interactions between vortices. In powders, the value of U(eff) does not depend on the size of particles. Measurements with ceramics give different values of U(eff) for samples prepared by using different heat treatment times. Finally, the temperature dependence of M(R)(T) is discussed within the framework of a vortex glass model. This approach is supported by a memory effect observed in M(R)(T).