Multiple order parameter configurations in superconductor/ferromagnet multilayers

Abstract

The coupling of two superconductors (S) through a ferromagnet (F) can lead to either a zero-or a π -phase difference between the superconducting banks. Most research in this area is performed on trilayer S/F/S film structures, in which two-order parameter configurations are possible. Increasing the number of layers and junctions leads to a larger number of possible configurations with, in principle, different properties such as the superconducting transition temperature T c . Here we study the behavior of a series of multilayers made of superconducting Nb and ferromagnetic Pd 81 Ni 19 . We find that for the individual layer thicknesses used, the transition width T c increases with increasing number of bilayers in the multilayer, in a well-defined manner. That the broadening is not simply due to increased disorder in the larger stacks, it is shown from x-ray diffraction, which finds very sharp interfaces for all samples; and from the effect of the magnetic field on the transition, which shows a considerable sharpening. We can make a connection with the various order parameter configurations using a matrix formulation of quasiclassical theory based on the Usadel equations and show that these different configurations take part in the Josephson networks, which are building up in the transition to the superconducting state.

Ubiquitous long-range antiferromagnetic coupling across the interface between superconducting and ferromagnetic oxides

“…While the understanding of S/F heterostructures based on classical low-T c metals has been progressing considerably [4][5][6] , a proper description of S/F oxide type interfaces is still lacking, although several intriguing interfacial phenomena have been reported [7][8][9][10] . To date, most work in this field has been focusing on the coupling of YBa 2 Cu 3 O 7-d (YBCO) and half-metallic manganites, like La 0.66 Ca 0.33 MnO 3 (LCMO) or La 0.66 Sr 0.33 MnO 3 (LSMO), being the superconducting and ferromagnetic layer, respectively.…”

Spectrums of Superconducting States and Triplet Effects in Superconductor/Ferromagnet Multilayers

“…In the S/F multilayers, the oscillations of the order parameter result in the possibility of a realization of spectra of superconductivity states, as was proved in [5][6][7][8]. In the previous works [5][6][7][8][9][10], it was shown how to realize experimentally a given superconductivity state. Here, we report some of the triplet effects that occur near the transition between states in the structures n[F/S]/F1/S0/F2/n[S/F] (n = 1, 2,) with the thin S0-layer and in-plane magnetized F-layers [10].…”

“…The devices of two types are based on these properties: the -contact elements of logical circuits for nanoelectronics, and the spin valves in spintronics [1][2][3][4][5]. In the S/F multilayers, the oscillations of the order parameter result in the possibility of a realization of spectra of superconductivity states, as was proved in [5][6][7][8]. In the previous works [5][6][7][8][9][10], it was shown how to realize experimentally a given superconductivity state.…”

“…Here, we report some of the triplet effects that occur near the transition between states in the structures n[F/S]/F1/S0/F2/n[S/F] (n = 1, 2,) with the thin S0-layer and in-plane magnetized F-layers [10]. The calculations have carried out within the framework of Usadel equations formalism [11], and the structure's material parameters, applied in the simulations, are close to that of Nb/PdNi system [7,8].…”

Evidence for aπjunction inNb/Ni0.96V0.04/Nbtrilayers revealed by superfluid

“…Thus, when ferromagnetism and superconductivity coexist, such as when Cooper pairs propagate into an adjacent ferromagnet in the proximity effect, competition between the two states creates several new possibilities for superconductivity. These include the famed oscillation of the amplitude of the order parameter known as the Fulde-Ferrell-Larkin-Ovchinnikov state (FFLO) [8,10,13,14], gapless superconductivity, [15] and π-junctions where the order parameter changes phase across the junction [2,16,17]. Such rich possibilities not otherwise found in superconductors or ferromagnets alone have led to both fundamental and practical interest in ferromagnetic/superconducting heterostructures, including as components of superconducting computational circuits [18].…”