Investigation of Current Gain in Superconducting-Ferromagnetic Transistors with High-jc Acceptor

Ivan P. Nevirkovets, Serhii Shafraniuk, Oleksandr Chernyashevskyy, Daniel T. Yohannes, Oleg A. Mukhanov, John B. Ketterson

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We report the results of a study of the current gain in high Josephson critical current density (jc ) superconductingferromagnetic transistors with the SISFIFS structure [where S, I, and F denote a superconductor (Nb), an insulator (AlOx), and a ferromagnetic material (permalloy, Py), respectively]. The Nb/AlOx/Nb trilayer, which serves as the acceptor (SIS) junction, is estimated to have Josephson critical current density jc of 19 kA/cm2. The Al/Py/Al/AlOx/Py/Al/Nb multilayer is deposited in a separate vacuum run after in situ ionmilling of about 8 nmof the top Nb layer. The devices are patterned using optical lithography and tested at 4.2 K. We have observed a small-signal current gain in the range of 5-9.We demonstrate that proper device engineering allows one to efficiently control the maximum Josephson current in the SISF acceptor junction using the quasiparticle injection.

Original languageEnglish (US)
Article number7779084
JournalIEEE Transactions on Applied Superconductivity
Issue number4
StatePublished - Jun 2017


  • Josephson effect
  • Superconducting-ferromagnetic hybrid structures
  • proximity effect
  • quasiparticle injection
  • superconducting transistor
  • superconductivity

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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