Investigation of the 0- π Phase Transition in Ferromagnetic Josephson Nanostructures

We investigate the Josephson current between two superconductors (S) which are connected through a diffusive magnetic junction with a complex structure Fc. Using the quantum circuit theory, we obtain the phase diagram of 0 and π Josephson couplings for Fc being an insulator-ferromagnet-insulator (IFI) double barrier junction or an IFNFI structure (where N indicates a normal-metal layer). Compared to a simple SFS structure, we find that the width of the transition, defined by the interval of exchange fields in which a 0-π transition is possible, is increased by insulating barriers at the interfaces and also by the presence of the additional N layer. The widest transition is found for symmetric Fc structures. The symmetric IFNFIS presents the most favorable condition to detect the temperatureinduced 0-π transition with a relative width, which is five times larger than that of the corresponding simple SFS structure.

Keywords:

Nano Structures , Ferromagnet , Josephson Current , 0-π Transition ,