Critical currents of ion-beam sputtered amorphous beryllium thin films and their application to an Abrikosov vortex memory

Critical current and flux pinning were examined for ion-beam sputtered (IBS) amorphous beryllium (a-Be) thin films with T_c 6 K. Pinning forces in IBS a-Be films were one or more than one order of magnitude smaller than those for crystalline superconductors, but were still rather large for amorphous superconductors. The viscosity coefficient for IBS a-Be was very small, 1-2×10^-9 N s/m², which was only a few tenths as large as viscosity coefficients for other metallic superconductors. Write operation characteristics for Abrikosov vortex memory with an IBS a-Be vortex storage region was tested. The write current level was reduced to about two thirds of that for fine-grained PbInAu previously reported. IBS a-Be films were proved to be a potential material for use in an Abrikosov vortex memory.