Critical current in SFIFS junctions

Abstract

Quantitative theory of the Josephson effect in SFIFS junctions (S denotes bulk superconductor, F - metallic ferromagnet, I - insulating barrier) is presented in the dirty limit. Fully self-consistent numerical procedure is employed to solve the Usadel equations at arbitrary values of the F-layers thicknesses, magnetizations, and interface parameters. In the case of antiparallel ferromagnets' magnetizations the effect of the critical current enhancement by the exchange field is observed, while in the case of parallel magnetizations the junction exhibits the transition to the pi-state. In the limit of thin F layers, we study these peculiarities of the critical current analytically and explain them qualitatively; the scenario of the 0-pi transition in our case differs from those studied before. The effect of switching between 0 and pi states by changing the F-layers' mutual orientation is demonstrated.Comment: 5 pages, 4 EPS figures; the style file jetpl.cls is included. Version 2: minor correction

Resonant peak in the density of states in normal-metal/diffusive-ferromagnet/superconductor junctions

“…We will show that in the former case the condition is equivalent to the one of Ref. 21 , while in the latter case the new condition is found. The calculation will be performed in the zero-temperature regime by varying the interface resistances as well as the resistance, the exchange field and the Thouless energy of the DF layer.…”

“…Experimentally DOS in F/S bilayers was measured by Kontos et al who found a broad DOS peak around zero energy when the π-phase shift occurs 22 . In diffusive ferromagnet/superconductor (DF/S) junctions the zeroenergy DOS may have a sharp peak 21 . However the conditions for the appearance of such anomaly have not been studied systematically so far.…”

“…Now let us discuss the weak proximity effect and derive the condition R d /R b ∼ 2h/E T h , following Ref. 21 . When spatial variation of θ is small, i.e., L ≪ D/ | ε ∓ h | (for the spin-up or spin-down subband respectively) and both R d /R b and R d /R ′ b are small (weak proximity effect), θ can be expanded as θ = θ 0 +θ 1 x+θ 2 x 2 where θ 1 , θ 2 ≪ θ 0 .…”

Josephson effect in double-barrier superconductor-ferromagnet junctions

“…12,13,20,21,22 However, a theory of the phase-coherent electronic transport in mesoscopic structures should be based on the solutions of Gor'kov or Bogoliubov-de Gennes (BdG) equations. The coherence effects have been studied recently for double-barrier SINIS junctions containing an interlayer of a clean nonmagnetic metal (N) with insulating interfaces (I), 23 and for FISIF junctions.…”

Proximity and Josephson effects in superconductor/antiferromagneticNb/γ−Fe50Mn50<

“…The various effects on the superconducting critical temperature, field and current density, (T C , H C and J C ), of the parallel and anti-parallel configurations of the F layers is of great interest. Various theoretical predictions have been made for J C enhancement in the case of S/F/X/F/S Josephson junctions, when the F layers have their moments switched from parallel to antiparallel, with large effects for X = insulator (I), [9,10,11], more weakly in the case of X = normal (dirty) metal (N) [12]. Spin torque on the F layers due to the Josephson current has been predicted for X = N [13].…”