Proximity effect in planar superconducting tunnel junctions containingNb∕NiCusuperconductor/ferromagnet bilayers

Abstract

We present experimental results concerning both the fabrication and characterization of superconducting tunnel junctions containing superconductor/ferromagnet ͑S/F͒ bilayers made by niobium ͑S͒ and a weak ferromagnetic Ni 0.50 Cu 0.50 alloy. Josephson junctions have been characterized down to T = 1.4 K in terms of current-voltage I-V characteristics and Josephson critical current versus magnetic field. By means of a numerical deconvolution of the I-V data the electronic density of states on both sides of the S/F bilayer has been evaluated at low temperatures. Results have been compared with theoretical predictions from a proximity model for S/F bilayers in the dirty limit in the framework of Usadel equations for the S and F layers, respectively. The main physical parameters characterizing the proximity effect in the Nb/ NiCu bilayer, such as the coherence length and the exchange field energy of the F metal, and the S/F interface parameters have been also estimated.

Time-resolved carrier dynamics and electron-phonon coupling strength in proximized weak ferromagnet-superconductor nanobilayers

“…24 and on the basis of our earlier investigations of Ni 0.50 Cu 0.50 / Nb bilayers, 25 we have evaluated S = 12 nm and F = 24 nm. Moreover, we numerically calculated the energy dependence of the local DoS at any position with respect to the F / S interface, as well as on both sides of the bilayer.…”

Properties of tunnel Josephson junctions with a ferromagnetic interlayer

“…Spontaneous phase shifts in S/F/S junctions were observed experimentally. [4][5][6][7][8][9][10][11][12][13][14][15] Superconductor / insulator / ferromagnet / superconductor ͑SIFS͒ junctions, i.e., S/F/S trilayers with one transparent interface and one tunnel barrier between S and F layers, represent practically interesting case of junctions. SIFS structure offers the freedom to tune the critical current density over a wide range and at the same time to realize high values of a product of the junction critical current I c and its normal state resistance R N .…”

Proximity effects and finite-quasiparticle-lifetime effects in normal metal/ferromagnetic semiconductor/superconductor structures

“…Andreev reflection (AR) [2] process plays an important role in the proximity effect. Proximity effects in ferromagnet (FM)/SC structures have recently attracted much attention in experimental and theoretical investigations [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The electron (hole) and the AR hole (electron) in FM have opposite spins and different Fermi momentum, interference between their wave functions causes the induced superconducting order parameter F(x) [21] to have a damped oscillation [22,23].…”