@PhdThesis{diss_mods_00017427,
  author = 	{Himmel, Nico},
  title = 	{Josephson Junctions with Ferromagnetic Alloy Interlayer},
  year = 	{2015},
  publisher = 	{Christian-Albrechts-Universit{\"a}t zu Kiel},
  address = 	{Kiel},
  keywords = 	{NiCu; SiFe; tunnel junction; Tunnelkontakt},
  abstract = 	{Josephson junctions are used as active devices in superconducting electronics and quantum information technology.
Outstanding properties are their distinct non-linear electrical characteristics and a usually sinusoidal relation between the current and the superconducting phase difference across the junction. In general the insertion of ferromagnetic material in the barrier of a Josephson junction is associated with a suppression of superconducting correlations. But also new phenomena can arise which may allow new circuit layouts and enhance the performance of applications.
This thesis presents a systematic investigation for two concepts to fabricate Josephson junctions with a rather uncommon negative critical current. Such devices exhibit an intrinsic phase slip of Pi between the electrodes, so they are also known as Pi-junctions. Both studies go well beyond existing experiments and in one system a Pi-junction is shown for the first time.
All the thin film junctions are based on superconducting Nb electrodes. In a first approach, barriers made from Si and Fe were investigated with respect to the realisation of Pi-junctions by spin-flip processes. The distribution of Fe in the Si matrix was varied from pure layers to disperse compounds. The systematic fabrication of alloy barriers was facilitated by the development of a novel timing-based combinatorial sputtering technique for planetary deposition systems.
An orthogonal gradient approach allowed to create binary layer libraries with independent variations of thickness and composition.
Second, Nb | AlOx | Nb | Ni60Cu40 | Nb (SIsFS) double barrier junctions were experimentally studied for the occurrence of proximity effect induced order parameter oscillations. Detailed dependencies of the critical current density on the thickness of s-layer and F-layer were acquired and show a remarkable agreement to existing theoretical predictions.
Especially a variation of jc and IcRn by the s-layer thickness up to the value of nonmagnetic SIS junctions is notable.
Additionally information on the emergence of superconductivity with the s-layer thickness was acquired.},
  url = 	{https://macau.uni-kiel.de/receive/diss_mods_00017427},
  file = 	{:https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00006209/diss_nh.pdf:PDF},
  language = 	{en}
}