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Abstract: Large area arrays of through-thickness nanoscale pores have been milled intosuperconducting Nb thin films via a process utilizing anodized aluminum oxidethin film templates. These pores act as artificial flux pinning centers,increasing the superconducting critical current, Jc, of the Nb films. Byoptimizing the process conditions including anodization time, pore size andmilling time, Jc values approaching and in some cases matching theGinzburg-Landau depairing current of 30 MA-cm^2 at 5 K have been achieved - aJc enhancement over as-deposited films of more than 50 times. In the fielddependence of Jc, a matching field corresponding to the areal pore density hasalso been clearly observed. The effect of back-filling the pores with magneticmaterial has then been investigated. While back-filling with Co has beensuccessfully achieved, the effect of the magnetic material on Jc has been foundto be largely detrimental compared to voids, although a distinct influence ofthe magnetic material in producing a hysteretic Jc versus applied fieldbehavior has been observed. This behavior has been tested for compatibilitywith currently proposed models of magnetic pinning and found to be most closelyexplained by a model describing the magnetic attraction between the fluxvortices and the magnetic inclusions.



Author: Rafael B. Dinner, Adam P. Robinson, Stuart C. Wimbush, Judith L. MacManus-Driscoll, Mark G. Blamire

Source: https://arxiv.org/







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