Magnetic Properties of the Stack of HTSC Tapes in a Wide Temperature Range

The trapped field strength of HTSC stacks were measured in the temperature range T=4-80 K and dc magnetic fields up to 8 Т. A single 12 mm by 12 mm square samples were cut from commercial (RE)BCO tape 12 mm wide and then stacked together. The number of layers in the stacks was varied from n=5 to n=250. Trapped field strength was measured by means of Hall probe which was placed directly on the stacks surface. The dependences of remnant field strength Brem on number of layers in the stacks at different temperature Brem (n) as well as on temperature dependences Brem (T) at various n were obtained. It was found that Brem (n) dependences have a nonlinear character with a tendency to saturation for n > 60. The maximum remnant (trapped) field was found to be more than 2.5 Т at T=4 К. The relaxation of trapped field was studied also and it was determined that the rate of relaxation processes tends to decrease with the increase in a number of tapes in the stack. The correlation between dependency Brem (n) and dependency of magnetic levitation force measured at T=77 K at zero field cooling were found.