Memory characteristics of ring-shaped ceramic superconductors

The authors investigated the residual magnetic field characteristics of ring-shaped ceramic superconductors in a Y-Ba-Cu-O system with high T_c. The residual magnetic field of a ring with asymmetric current paths, supplied by external currents, appeared when one of the branch currents was above the critical current. The residual magnetic field saturated when both branch currents exceeded the critical current of the ring and showed hysteresis-like characteristics. The saturated magnetic field is subject to the critical current of the ring. The time constant of the persistent current in a ring, evaluated from the damping coefficient, was 5000 hours at most. A superconducting ring with asymmetric current paths suggests a simple, novel persistent-current-type memory device