Аннотация:We have studied different types of Magnetic Josephson Junctions (MJJs) for a scalable high-density cryogenic memory compatible with energy-efficient single flux quantum (SFQ) circuits. We fabricated single ferromagnetic layer barrier Nb-Al/AlOx-Nb-PdFe–Nb junctions with different sizes down to 3x3 μm2. It was shown experimentally that these devices could be switched between superconducting and resistive states with corresponding high and low critical currents using short magnetic pulses using the integrated superconducting control line.
We also present the first realization of MJJs with barrier containing two ferromagnetic layers F1 and F2 separated by a thin layer of a superconductor. We present results of experimental evaluation of these double barrier MJJs based on PdFe layers of different thicknesses. In the frame of Usadel equations, we have calculated dependencies of the structures critical current, Ic, upon temperature, thickness of the layers, transparencies of interfaces and mutual orientation of magnetization vectors of F1 and F2 films. Theoretical study shows that there is the set of parameters under which the state of intermediate layer depends on mutual orientation of F1 and F2 layers, namely it is high critical current for antiparallel orientation and low critical current for parallel one. The effect of this phase transition on the Ic is studied in detail. We compare and discuss our experimental and theoretical results.