575 research outputs found
Manifestation of the odd-frequency spin-triplet pairing state in diffusive ferromagnet / superconductor junctions
Using the quasiclassical Green's function formalism, we study the influence
of the odd-frequency spin-triplet superconductivity on the local density of
states (LDOS) in a diffusive ferromagnet (DF) attached to a superconductor.
Various possible symmetry classes in a superconductor are considered which are
consistent with the Pauli's principle: even-frequency spin-singlet even-parity
(ESE) state, even-frequency spin-triplet odd-parity (ETO) state, odd-frequency
spin-triplet even-parity (OTE) state and odd-frequency spin-singlet odd-parity
(OSO) state. For each of these states, the pairing state in DF is studied.
Particular attention is paid to the study of spin-singlet s-wave and
spin-triplet p-wave superconductors as the examples of ESE and ETO
superconductors. For spin-singlet case the magnitude of the OTE component of
the pair amplitude is enhanced with the increase of the exchange field in DF.
When the OTE component is dominant at low energy, the resulting LDOS in DF has
a zero energy peak (ZEP). On the other hand, in DF / spin-triplet p-wave
superconductor junctions LDOS has a ZEP in the absence of the exchange field,
where only the OTE paring state exists. With the increase of the exchange
field, the ESE component of the pair amplitude induced in DF is enhanced. Then,
the resulting LDOS has a ZEP splitting. We demonstrate that the appearance of
the dominant OTE component of the pair amplitude is the physical reason of the
emergence of the ZEP of LDOS.Comment: 9 pages, 9 figure
Antiferromagnetic resonances in superconductor-ferromagnet multilayers
In this work, we study magnetization dynamics in superconductor-ferromagnet
(S-F) thin-film multilayer. Theoretical considerations supported by the
broad-band ferromagnetic resonance spectroscopy reveal development of acoustic
and optic resonance modes in S-F multilayers at significantly higher
frequencies in comparison to the Kittel mode of individual F-layers. These
modes are formed due to antiferromagnetic-like interaction between F-layers via
shared circulating superconducting currents in S-layers. The gap between
resonance modes is determined by the thickness and superconducting penetration
depth in S-layers. Overall, rich spectrum of S-F multilayers and its tunability
opens wide prospects for application of these multialyers in magnonics as well
as in various superconducting hybrid systems.Comment: 5 pages, 4 figures, 34 reference
Stray-fields-based magnetoresistance mechanism in Ni80Fe20-Nb-Ni80Fe20 trilayers
We report on the transport and magnetic properties of hybrid trilayers and
bilayers that consist of low spin-polarized Ni80Fe20 exhibiting in-plane but no
uniaxial anisotropy and low-Tc Nb. We reveal a magnetoresistance effect that is
pronounced. In our trilayers the magnetoresistance exhibits an increase of two
orders of magnitude when the superconducting state is reached: from the
conventional normal-state values 0.6 % it goes up to 1000 % for temperatures
below Tc. In contrast, in the bilayers the effect is only minor since from 3%
in the normal state increases only to 70 % for temperatures below Tc.
Magnetization data of both the longitudinal and transverse magnetic components
are presented. Most importantly, we present data not only for the normal state
of Nb but also in its superconducting state. Strikingly, these data show that
below its Tc SC the Nb interlayer under the influence of the outer Ni80Fe20
layers attains a magnetization component transverse to the external field. By
comparing the transport and magnetization data we propose a candidate mechanism
that could motivate the pronounced magnetoresistance effect observed in the
trilayers. Adequate magnetostatic coupling of the outer Ni80Fe20 layers is
motivated by stray fields that emerge naturally in their whole surface due to
the multidomain magnetic structure that they attain near coercivity. Atomic
force microscopy is employed in order to examine the possibility that such
magnetostatic coupling could be promoted by interface roughness. Referring to
the bilayers, although out-of-plane rotation of the magnetization of the single
Ni80Fe20 layer is still observed, in these structures magnetostatic coupling
does not occur due to the absence of a second Ni80Fe20 one so that the observed
magnetoresistance peaks are only modest.Comment: 9 pages, 7 figure
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