Investigation of glass behaviour of vortex arrays in superconducting submicron YBCO powders by magnetic relaxation measurements
Magnetic relaxation measurements are made in the remanent state of pure and Zn-doped submicron YBCO powders. A characteristic feature of these samples is dipolar interaction between single vortices trapped in different particles. Similar to other systems with dipolar interactions, such as powders of fine ferromagnetic particles, our samples show glassy behaviour: different metastable states with various pinning properties can be prepared by varying the strength of the magnetizing field, i.e. history of the sample. It is found also that the relation between the pinning energy and the magnetic moment can be described by an expression similar to the vortex glass interpolation formula.