Depairing critical current achieved in superconducting thin films with through-thickness arrays of artificial pinning centers

Large area arrays of through-thickness nanoscale pores have been milled into superconducting Nb thin films via a process utilizing anodized aluminum oxide thin film templates. These pores act as artificial flux pinning centers, increasing the superconducting critical current, Jc, of the Nb films. By optimizing the process conditions including anodization time, pore size and milling time, Jc values approaching and in some cases matching the Ginzburg–Landau depairing current of 30 MA cm − 2 at 5 K have been achieved—a Jc enhancement over as-deposited films of more than 50 times. In the field dependence of Jc, a matching field corresponding to the areal pore density has also been clearly observed. The effect of backfilling the pores with magnetic material has then been investigated. While backfilling with Co has been successfully achieved, the effect of the magnetic material on Jc has been found to be largely detrimental compared to voids, although a distinct influence of the magnetic material in producing a hysteretic Jc versus applied field behavior has been observed. This behavior has been tested for compatibility with currently proposed models of magnetic pinning and found to be most closely explained by a model describing the magnetic attraction between the flux vortices and the magnetic inclusions.

[1]  J. Heath,et al.  Achieving the theoretical depairing current limit in superconducting nanomesh films. , 2010, Nano letters.

[2]  I. Lyuksyutov,et al.  Flux pinning with a magnetic nanorod array , 2010 .

[3]  M. Blamire,et al.  Enhanced critical current in YBa2Cu3O7−δ thin films through pinning by ferromagnetic YFeO3 nanoparticles , 2010 .

[4]  S. Mátéfi-Tempfli,et al.  High magnetic field matching effects in NbN films induced by template grown dense ferromagnetic nanowires arrays , 2009 .

[5]  Matthew B. Johnson,et al.  Sequential vortex hopping in an array of artificial pinning centers , 2009 .

[6]  M. Blamire,et al.  Superconductor–ferromagnet nanocomposites created by co-deposition of niobium and dysprosium , 2009, 0903.3142.

[7]  V. V. Moshchalkov,et al.  Nucleation of superconductivity and vortex matter in superconductor–ferromagnet hybrids , 2009, 0902.1630.

[8]  M. Blamire,et al.  Critical current enhancement by Lorentz force reduction in superconductor–ferromagnet nanocomposites , 2009 .

[9]  J. MacManus‐Driscoll,et al.  Large-area silica nanotubes with controllable geometry on silicon substrates , 2009 .

[10]  J. MacManus‐Driscoll,et al.  Self-assembled, rare earth tantalate pyrochlore nanoparticles for superior flux pinning in YBa2Cu3O7−δ films , 2009 .

[11]  I. Schuller,et al.  Superconducting vortex pinning with artificial magnetic nanostructures , 2008 .

[12]  J. MacManus‐Driscoll,et al.  Controlled, perfect ordering in ultrathin anodic aluminum oxide templates on silicon , 2007 .

[13]  Q. Jia,et al.  Materials science challenges for high-temperature superconducting wire. , 2007, Nature materials.

[14]  M. Blamire,et al.  Hysteretic vortex pinning in superconductor-ferromagnet nanocomposites. , 2007, Physical review letters.

[15]  P. Sacramento,et al.  Vorticity and magnetic shielding in a type-II superconductor , 2005, Journal of physics. Condensed matter : an Institute of Physics journal.

[16]  V. Moshchalkov,et al.  Nucleation of superconductivity and vortex matter in hybrid superconductor/ferromagnet nanostructures , 2006 .

[17]  Michael Siegel,et al.  Dependence of magnetic penetration depth on the thickness of superconducting Nb thin films , 2005 .

[18]  I. Lyuksyutov,et al.  Ferromagnet–superconductor hybrids , 2004, cond-mat/0409137.

[19]  R. Prozorov,et al.  Magnetic nanoparticles as efficient bulk pinning centers in type-II superconductors , 2004, cond-mat/0403015.

[20]  Q. X. Jia,et al.  Strongly enhanced current densities in superconducting coated conductors of YBa2Cu3O7–x + BaZrO3 , 2004, Nature materials.

[21]  F. Peeters,et al.  Vortex pinning in a superconducting film due to in-plane magnetized ferromagnets of different shapes: The London approximation , 2004 .

[22]  V. Moshchalkov,et al.  Nanoengineered magnetic-field-induced superconductivity. , 2002, Physical review letters.

[23]  D. Physics,et al.  Superconducting transition and vortex pinning in Nb films patterned with nanoscale hole arrays , 2002, cond-mat/0204535.

[24]  Hsueh-Chia Chang,et al.  Nanoscale pore formation dynamics during aluminum anodization. , 2002, Chaos.

[25]  Lingchuan Li.  Influence of phosphorous acid on electrodeposition of cobalt in pores of porous anodic films of aluminum , 2001 .

[26]  J. Ketterson,et al.  Asymmetric flux pinning in a regular array of magnetic dipoles , 1998 .

[27]  F. Keller,et al.  Structural Features of Oxide Coatings on Aluminum , 1953 .