Magnetic relaxation in hard type-II superconductors
Magnetic relaxation in a type-II superconductor is simulated for a range of temperatures T in a simple model of the 2D Josephson junction array (JJA) with finite screening. The high-T phase, that is characterised by a single time scale τα, crosses over to an intermediate phase at a lower temperature Tcr wherein a second time scale τβ Jc) to sub-critical (J < Jc) state separated by an intermediate state with frozen dynamics is observed. Both τα and τβ diverge at Tsc < Tcr, marking the transition into a state with true persistent current.