16 research outputs found
Enhancement of the Josephson current by magnetic field in superconducting tunnel structures with paramagnetic spacer
The dc Josephson critical current of a (S/M)IS tunnel structure in a parallel
magnetic field has been investigated (here S is a superconductor, S/M is the
proximity coupled S and paramagnet M bilayer and I is an insulating barrier).
We consider the case when, due to the Hund's rule, in the M metal the effective
molecular interaction aligns spins of the conducting electrons antiparallel to
localized spins of magnetic ions. It is predicted that for tunnel structures
under consideration there are the conditions when the destructive action of the
internal and the applied magnetic fields on Cooper pairs is weakened and the
increase of the applied magnetic field causes the field-induced enhancement of
the tunnel critical current. The experimental realization of this interesting
effect of the interplay between superconductivity and magnetism is also
discussed.Comment: 5 pages 3 figure
Josephson current in a superconductor-ferromagnet junction with two non-collinear magnetic domains
We study the Josephson effect in a
superconductor--ferromagnet--superconductor (SFS) junction with ferromagnetic
domains of non-collinear magnetization. As a model for our study we consider a
diffusive junction with two ferromagnetic domains along the junction. The
superconductor is assumed to be close to the critical temperature , and
the linearized Usadel equations predict a sinusoidal current-phase relation. We
find analytically the critical current as a function of domain lengths and of
the angle between the orientations of their magnetizations. As a function of
those parameters, the junction may undergo transitions between 0 and
phases. We find that the presence of domains reduces the range of junction
lengths at which the phase is observed. For the junction with two domains
of the same length, the phase totally disappears as soon as the
misorientation angle exceeds . We further comment on possible
implication of our results for experimentally observable 0-- transitions
in SFS junctions.Comment: 9 pages, 4 figures, minor changes, references adde
Josephson Current in S-FIF-S Junctions: Nonmonotonic Dependence on Misorientation Angle
Spectra and spin structures of Andreev interface states in S-FIF-S junctions
are investigated with emphasis on finite transparency and misorientation angle
between in-plane magnetizations of ferromagnetic layers in a three-layer
interface. It is demonstrated that the Josephson current in S-FIF-S quantum
point contacts can exhibit a nonmonotonic dependence on the misorientation
angle. The characteristic behavior takes place, if the pi-state is the
equilibrium state of the junction in the particular case of parallel
magnetizations.Comment: 5 pages, 4 figure
Magnetic exchange interaction induced by a Josephson current
We show that a Josephson current flowing through a
ferromagnet-normal-metal-ferromagnet trilayer connected to two superconducting
electrodes induces an equilibrium exchange interaction between the magnetic
moments of the ferromagnetic layers. The sign and magnitude of the interaction
can be controlled by the phase difference between the order parameters of the
two superconductors. We present a general framework to calculate the Josephson
current induced magnetic exchange interaction in terms of the scattering
matrices of the different layers. The effect should be observable as the
periodic switching of the relative orientation of the magnetic moments of the
ferromagnetic layers in the ac Josephson effect.Comment: 12 pages, 7 figure