A. F. Volkov

Odd triplet superconductivity and related phenomena in superconductor-ferromagnet structures

This review considers unusual effects in superconductor-ferromagnet structures, in particular, the triplet component of the condensate generated in those systems. This component is odd in frequency and even in momentum, which makes it insensitive to nonmagnetic impurities. If the exchange field is not homogeneous in the system, the triplet component is not destroyed even by a strong exchange field and can penetrate the ferromagnet over long distances. Some other effects considered here and caused by the proximity effect are enhancement of the Josephson current due to the presence of the ferromagnet, induction of a magnetic moment in superconductors resulting in a screening of the magnetic moment, and formation of periodic magnetic structures due to the influence of the superconductor. Finally, theoretical predictions are compared with existing experiments.

Enhancement of the Josephson Current by an Exchange Field in Superconductor-Ferromagnet Structures

We calculate the dc Josephson current for two superconductor/ferromagnet (S/F) bilayers separated by a thin insulating film. It is demonstrated that the critical Josephson current I(c) in the junction strongly depends on the relative orientation of the effective exchange field h of the bilayers. We found that in the case of an antiparallel orientation I(c) increases at low temperatures with increasing h and at zero temperature has a singularity when h equals the superconducting gap Delta. This striking behavior contrasts with the suppression of the critical current by the magnetic moments aligned in parallel and is an interesting new effect of the interplay between superconductors and ferromagnets.

Superconducting Phase Coherent Electron Transport in Proximity Conical Ferromagnets

We report superconducting phase-periodic conductance oscillations in ferromagnetic wires with interfaces to conventional superconductors. The ferromagnetic wires were made of Ho, a conical ferromagnet. The distance between the interfaces was much larger than the singlet superconducting penetration depth. We explain the observed oscillations as due to the long-range penetration of an unusual helical triplet component of the order parameter that is generated at the superconductor/ferromagnet interfaces and maintained by the intrinsic rotating magnetization of Ho.

Josephson current in superconductor-ferromagnet structures with a nonhomogeneous magnetization

We calculate the dc Josephson current

Induced ferromagnetism due to superconductivity in superconductor-ferromagnet structures

{I}_{J}

Reentrance of the Metallic Conductance in a Mesoscopic Proximity Superconductor

for two types of superconductor-ferromagnet (S/F) Josephson junctions. The junction of the first type is a S/F/S junction. On the basis of the Eilenberger equation, the Josephson current is calculated for an arbitrary impurity concentration. If

Local density of states in superconductor-strong ferromagnet structures

h\ensuremath{\tau}\ensuremath{\ll}1,

On the contribution of the superconductor to the resistance of a superconductor-normal metal system

the expression for the Josephson critical current

Spin screening of magnetic moments in superconductors

{I}_{c}

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

is reduced to that which can be obtained from the Usadel equation