Crossover between short and long range proximity effects in SFS junctions with Ni-based ferromagnets

Abstract

We study Superconductor/Ferromagnet/Superconductor junctions with CuNi, PtNi, or Ni interlayers. Remarkably, we observe that supercurrents through Ni can be significantly larger than through diluted alloys. The phenomenon is attributed to the dirtiness of disordered alloys leading to a short coherence length despite a small exchange energy. To the contrary, pure Ni is clean resulting in a coherence length as long as in a normal metal. Analysis of temperature dependencies of critical currents reveals a crossover from short (dirty) to long (clean) range proximity effects in Pt1-xNix with increasing Ni concentration. Our results point out that structural properties of a ferromagnet play a crucial role for the proximity effect and indicate that conventional strong-but-clean ferromagnets can be advantageously used in superconducting spintronic devices.

14 pages, 8 figures

References in corpus (9)

• A spin triplet supercurrent through the half-metallic ferromagnet CrO2
• Superconducting triplet spin valve
• Josephson tunnel junctions with strong ferromagnetic interlayer
• Controllable generation of a spin-triplet supercurrent in a Josephson spin-valve
• Generalized quasiclassical theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets
• Anisotropic intrinsic anomalous Hall effect in ordered 3dPt alloys
• Long ranged singlet proximity effect in ferromagnetic nanowires
• Observation of the dominant spin-triplet supercurrent in Josephson spin valves with strong Ni ferromagnets
• The anti-ordinary Hall effect in NiPt thin films