Josephson tunnel junctions with a strong ferromagnetic interlayer

Abstract

The dependence of the critical current density j c on the ferromagnetic interlayer thickness d F was determined for Nb/ Al 2 O 3 / Cu/ Ni/ Nb Josephson tunnel junctions with ferromagnetic Ni interlayer thicknesses from very thin films ͑ϳ1 nm͒ upward and classified into F-layer thickness regimes showing a dead magnetic layer, exchange, exchange+ anisotropy and total suppression of j c . The Josephson coupling changes from 0 to as function of d F , and-very close to the crossover thickness-as function of temperature. The strong suppression of the supercurrent in comparison to nonmagnetic Nb/ Al 2 O 3 / Cu/ Nb junctions indicated that the insertion of a F layer leads to additional interface scattering. The transport inside the dead magnetic layer was in dirty limit. For the magnetically active regime fitting with both the clean and the dirty limit theories was carried out, indicating dirty limit condition, too. The results were discussed in the framework of literature.

Visualizing supercurrents in ferromagnetic Josephson junctions with various arrangements of 0 andπsegments

“…Such π junctions are now intensively investigated, as they have a great potential for applications in a broad range of devices ranging from classical digital circuits [2,3,4,5] to quantum bits [6,7,8,9]. Nowadays, π Josephson junctions can be fabricated by various technologies, including junctions with a ferromagnetic barrier [10,11,12,13,14,15,16,17,18], quantum dot junctions [19,20,21] and nonequilibrium superconductor-normal metal-superconductor Josephson junctions [22,23,24] In the simplest case the supercurrent density j s across the junctions is given by the first Josephson relation…”

Electronic transport through ferromagnetic and superconducting junctions with spin-filter tunneling barriers

“…On the one hand, this interest is due to the progress in technology that allows a controllable fabrication of nanohybrid systems using a wide range of superconducting and magnetic materials. On the other hand, this interest is due to the discovery of new and interesting fundamental phenomena, as for example the so-called π state in S/F /S Josephson junctions [1][2][3][4][5][6][7][8][9] and more recently the long-range proximity effect mediated by odd-frequency triplet superconducting correlations in S/F structures [10][11][12][13][14][15][16][17] (for an overview, see Refs. [18][19][20][21][22].…”

Giant triplet proximity effect in superconducting pseudo spin valves with engineered anisotropy

“…The key to this process is magnetic inhomogeneity at the S-F interface. For example, consider a S-F -F-F -S Josephson junction [7]: If the F and F layer magnetizations are collinearly aligned, spin-zero triplet pairs form which, like singlet pairs, are short ranged [8] with a coherence length in F metals of only a few nanometers (Ni [9][10][11][12], NiFe [13,14], Co [11,15,16], and Fe [17,18]). However, if F and F layer magnetizations are noncollinearly aligned spin-one triplet pairs form and the coherence length is greatly extended [19][20][21][22][23][24][25][26][27].…”