DC and RF measurements of superconducting-ferromagnetic multi-terminal devices

We report experimental results of the DC and RF characterization of multi-terminal SFIFSIS devices (where S, I, and F denote a superconductor (Nb), an insulator (AlO
_x
), and a ferromagnetic material (Ni), respectively), which display transistor-like properties. Applying a 0.2 MHz signal in addition to a constant DC bias current to the injector (SFIFS) junction, we observe a voltage gain of ~1.25 on the acceptor SIS junction, if operation point of the SIS junction is chosen in the sub-gap region of its current-voltage characteristic. We also observed a good input-output isolation of our SFIFSIS devices of the order of 30 dBV. The experiments indicate that, after optimization of the geometry and improvement of junction quality, these devices can be used as input-output isolators and amplifiers for memory, digital and RF applications.