FLUX-CREEP IN SUPERCONDUCTING FILMS - AN EXACT SOLUTION

An exact solution of the nonlinear integral equation is obtained that describes flux creep in strips or disks. We calculate both analytically and numerically the relaxation of the electric field E(r, t), sheet current J (r, t), flux density B (r, t), and magnetic moment M (t). After some transient period, E(r, t) approaches a universal nonmonotonic shape, regardless of the detailed form of the current-voltage law E(J). We predict that, in spite of the relaxation of M, B(r, t) will both increase and decrease with t in regions separated by ''neutral lines,'' along which B(r, t) does not depend on time.