Flux pinning by twin planes in Nd-123 and Y-123 single crystals

The pinning by twin planes and an isotropic pinning disorder was investigat ed on single crystals of NdBa2Cu3O7-delta and YBa2Cu3O7-delta a studying th e angular dependence of total magnetic moment measured quasistatically by m eans of SQUID and dynamically by means of a vibrating sample magnetometer. The field dependence of the normalized relaxation rate of the vortex system pinned by twin planes, and by a random isotropic pinning disorder was dete rmined. The qualitative difference of the two field profiles is clearly ref lected by the shapes of the corresponding magnetic hysteresis loops. Materi al aspects of the pinning and the effect of the measurement method are disc ussed. (C) 2000 Elsevier Science B.V. All rights reserved.