Flux avalanches in Nb superconducting shifted strip arrays

Abstract

Abstract. Flux penetrations into three-dimensional Nb superconducting strip arrays, where two layers of strip array are stacked by shifting a half period, are studied by using magneto-optical imaging method. Flux avalanches are observed when the overlap between the top and bottom layers is large even if the width of each strip is well below the threshold value. In addition, anomalous linear avalanches perpendicular to the strip are observed in the shifted strip array when the overlap is very large and the thickness of superconductor is greater than the penetration depth. We discuss possible origins of the flux avalanches including the linear ones by considering the flux penetration calculated by the Campbell method assuming the Bean model.

Controlling magnetic flux penetration in low-T C superconducting films and hybrids

“…Flux avalanches have also been observed in threedimensional superconducting structures. Tamegai and co-authors [174][175][176] have prepared 3D stacks of superconducting strip arrays varying the number of overlapping and adjacent layers, as well as the thicknesses of both the superconducting and the insulating layers. They observed using MOI that the flux avalanche morphology depends on the overlapping between the neighbor layers: for small overlap, spotlike shapes; for large overlap, long fingerlike avalanches traversing many strips in different layers.…”

Inductive braking of thermomagnetic avalanches in superconducting films

“…From there, the avalanche invades an area that grows into a dendritic structure. The residual flux patterns from such events have been observed in many materials, e.g., Pb [1,2], Sn [3], Nb [4,5], YBa 2 Cu 3 O 7−x [6,7], MgB 2 [8][9][10], Nb 3 Sn [11], YNi 2 B 2 C [12], NbN [13], and a-MoGe [14]. Theory suggests that these avalanches are nucleated by a thermomagnetic instability, where a fluctuation-induced increase in temperature facilitates uncontrolled penetration of magnetic flux [15,16].…”

Block copolymer self-assembly–directed synthesis of mesoporous gyroidal superconductors

“…Despite a growing interest in mesoscale science ( 7 ), only a few studies to date have pursued these phenomena. For example, there have been reports of a superconducting oxide asymmetric membrane with a mesoporous layer on a macroporous substrate ( 8 ), a sputtered superconducting Nb layer on a nanoporous Si substrate ( 9 ), lithographically fabricated Nb-shifted strip arrays ( 10 ), and biotemplated oxide superconductors with micrometer-scale structural ordering ( 11 ). The sparsity of such studies is attributable, in part, to a lack of synthetic approaches to mesostructured superconductors that allow systematic investigations of the effects of mesostructure on superconductivity.…”