Matching in flux-line lattice pinned by triangular pinning array with disorder

The interaction of a flux line lattice (FLL) with quasiperiodic pinning arrays recently attracted a lot of attention. A different type of order is found for self-organized patterns, as, e.g., a weakly disturbed FLL itself, which is characterized by a short-range triangular order but a missing directional long-range order. We prepared arrays of nanoscaled artificial pinning centers (APCs) with such order into Nb thin films. The APCs are formed by depositing Nb onto substrates covered with Si nanopillars or metal nanospheres with diameters of 10 - 50 nm. The mutual distance of pillars and spheres is about 100 nm. Nanospheres are produced by using the self-organization of inverse micelles formed by diblock-copolymers, whose core is loaded with a metal precursor, e.g., Au or FePt. Si nanopillars are formed by using an array of gold nanospheres as an etching mask during reactively ion etching a Si substrate. In this way, the pattern of the nanoparticle array is transferred onto the Si substrate. The resulting lattice of APCs, formed by the Si pillars or metal nanospheres perforating the Nb film, mirrors the order of the micellar array. By nanoshaping APCs of different types, sizes and mutual distances, we can investigate specific influences on magnetic and electrical transport properties. (orig.)