▎ 摘　　要

The Josephson current in a double ferromagnetic layer SG/F-1/F-2/SG graphene junction where the SG's are graphene-based s-wave superconductors and the F-1,F-2 are ferromagnetic layers of thicknesses d(1,2) in which the exchange energies are E-ex1,E-2, is studied. The Josephson current in this junction is composed of Cooper pairs formed by quasi particles which are massless Weyl-Dirac electrons. By switching the alignment of the two exchange fields, we find that the Josephson current in the junction can change from being in the pi-state to being in the 0-state. For the case where the magnitudes of the exchange field strength are the same, it is seen that the phase difference dependence of the critical Josephson current in a parallel aligned junction indicated a cross over from a 0-state to pi-state whenever the ferromagnetic barrier strength chi(ex) is equal to (n/2 + 0.25)pi (with n = 1, 2,...). The AP-junction for F-1 = F-2 behaves as if it has no the magnetic barriers, like S/N/S junction. It is also seen that the temperature dependence of the (%) magneto-Josephson current ratio defined as the difference between the critical currents of the graphene-based P-junction and AP-junctions defined as, %P-S similar to (100%)x(I-P(c) - I-AP(c))/I-P(c), is found to be oscillated under varying the exchange energies. The maximum value of %P-S, (max)P-S -> infinity as T -> T-C. The cause of these effects is the relativistic nature of the quasi particles in the graphene-based junctions. (C) 2009 Elsevier B.V. All rights reserved.