Width of the 0-pi phase transition in diffusive magnetic Josephson junctions

Abstract

We investigate the Josephson current between two superconductors (S) which are connected through a diffusive magnetic junction with a complex structure (F-c). Using the quantum circuit theory, we obtain the phase diagram of 0 and pi Josephson couplings for F-c 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-pi 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 F-c structures. The symmetric SIFNFIS presents the most favorable condition to detect the temperature-induced 0-pi transition with a relative width, which is five times larger than that of the corresponding simple SFS structure.