No abstract

No abstract

We demonstrate that a square lattice of artificial pinning centers in a superconducting Nb film induces the formation of highly ordered interstitial vortex phases with different symmetries for external magnetic fields as high as the eighth matching field. These ''supermatching'' phases are identified by distinct differences in the behavior of their critical currents, magnetoresistivity, and magnetization. Our results are consistent with predictions of supermatching lattice symmetries by recent numerical simulations. ͓S0163-1829͑99͒51142-9͔ RAPID COMMUNICATIONS R12 586 PRB 60 V. METLUSHKO et al. RAPID COMMUNICATIONS PRB 60 R12 587 INTERSTITIAL FLUX PHASES IN A . . . RAPID COMMUNICATIONS R12 588 PRB 60 V. METLUSHKO et al.

Nb films containing extended arrays of holes with 45-nm diameter and 100-nm spacing have been fabricated using anodized aluminum oxide (AAO) as substrate. Pronounced matching effects in the magnetization and Little-Parks oscillations of the superconducting critical temperature have been observed in fields up to 9 kOe. Flux pinning in the patterned samples is enhanced by two orders of magnitude as compared to unpatterned reference samples in applied fields exceeding 5 kOe. Matching effects are a dominant contribution to vortex pinning at temperatures as low as 4.2 K due to the extremely small spacing of the holes.

No abstract