Measurement of flux creep in Bi2Sr2CaCu2O8 using electron spin resonance

Type II superconductivity

“…Plots of the magnetization versus the logarithm of time tend to be linear, with flux continuing to enter the sample several hours later. Figure 9.34 shows the time dependence of the magnetization in a superconductor that was zerofield-cooled then exposed to a 5 T field that was subsequently decreased to 3 T. In this experiment (Kung et al, 1992; see also Pencarinha et al, 1995), the time dependence of the magnetization of YBa 2 Cu 3 O 7 containing Y 2 BaCuO 5 particles (green phase) functioning as pinning centers to enhance J c was monitored for several hours 403 Type II superconductivity after the field had been reduced to 3 T. Experimental results are shown for temperatures between 5 and 50 K. Similar results have been obtained with an electron spin resonance surface probe technique (Pencarinha et al, 1995). We see from the figure that the magnetization is greater in magnitude and decays faster at the lower temperatures.…”

“…If the pinning forces are not Figure 9.34 Magnetic relaxation of YBa 2 Cu 3 O 7 in a 3 T field showing the linear dependence of magnetization on the logarithm of time for temperatures between 5 and 50 K (Kung et al, 1992; see also Pencarinha et al, 1995). 404 Superconductivity sufficiently strong to prevent flux motion (i.e., the superconductor is soft) then the following occurs:…”

Vortex Excitations Above T c in the Cuprate Superconductor Bi2Sr2Ca2Cu3O10 as Revealed by ESR

“…First, since the crystal thickness is by order of magnitude less than its plane dimension, the demagnetization factor is very small, N ≪ 1. So the field increase near the surface and the relative signal shift can not be considerable 29 . Second, in the vortex state some of the vortex lines bend near the edges and run both through the surface perpendicular to applied field and through parallel surface with DPPH deposited on it (Fig.…”