NOVEL FLUX PHASES IN SUPERCONDUCTORS WITH A PERIODIC PINNING ARRAY

Flux-line confinement by triangular and square regular arrays of micro holes (''antidots'') has been studied in superconducting films (Pb, WG e) and multilayers (Pb/Ge). For relatively large antidots sharp cusp-l ike magnetization anomalies appear at the matching fields Hm. These an omalies are caused by the formation of the multi-quanta vortex lattice s at each subsequent Hm. The multi-quanta vortex lattices make possibl e a peacefull coexistence of the flux penetration at the antidots and the presence of a substantial superfluid density in the space between them. This leads to a very strong enhancement of the critical current density in films with an antidot lattice. For smaller antidots the vor tices are forced to occupy the interstitial positions after the satura tion of the pinning sites at antidots. This leads to the formation of the novel composite flux-line lattices consisting from the interpenetr ating sublattices of weakly pinned interstitial single-quantum vortice s and multi-quanta vortices strongly pinned by the antidots. When the interstitial flux-line lattice melts, it forms the interstitial flux l iquid coexisting with the flux solid at antidots.