共查询到20条相似文献,搜索用时 15 毫秒
1.
P. V. Leksin A. A. Kamashev N. N. Garif’yanov A. A. Validov Ya. V. Fominov J. Schumann V. E. Kataev B. Büchner I. A. Garifullin 《Physics of the Solid State》2016,58(11):2165-2176
An important role of the morphology of a superconducting layer in the superconducting spin-valve effect has been established. The triplet pairing induced by the superconductor/ferromagnet proximity effect has been experimentally investigated for samples CoOx/Py1/Cu/Py2/Cu/Pb (where Py = Ni0.81Fe0.19) with a smooth superconducting layer. The optimization of the parameters of this structure has demonstrated a complete switching between the normal and superconducting states with a change in the relative orientation of magnetizations of the ferromagnetic layers from the antiparallel to orthogonal orientation. A pure triplet contribution has been observed for the sample with a permalloy layer thickness at which the superconducting spin-valve effect vanishes. A direct comparison of the experimental data with the theoretical calculation of the temperature of the transition to the superconducting state has been performed for the first time. 相似文献
2.
Ferromagnet/superconductor/ferromagnet (F/S/F) spin-valve systems in the dirty limit, described by Usadel equations, was theoretically investigated with respect to superconducting transition temperature. Their superconducting characteristics strongly depend not only on the mutual orientation and thickness of the ferromagnetic layers, but also on the interface transparency as well as magnetic scattering. Especially, the introduction of magnetic scattering drastically reduces the spin-valve effect in our work. The obtained results could be used to understand experimental values of and to provide guidelines for optimizing the experimental systems. 相似文献
3.
I. A. Garifullin 《JETP Letters》2011,93(10):612-621
The recent experimental results on the proximity effect in heterostructures composed of superconducting and ferromagnetic
thin films are reviewed. First, the experimental observation and investigation of the spin screening effect, i.e., a spin
polarization in the V layer developing in the superconducting state under the influence of a spin polarization of conduction
electrons in the ferromagnetic layer are discussed. This effect was predicted theoretically by Bergeret et al. [F. S. Bergeret,
A. F. Volkov, and K. B. Efetov, EPL 66, 111 (2004); Phys. Rev. B 69, 174504 (2004)]. Then, the progress concerning the experimental realization of the superconducting spin switch device based
on the superconductor/ferromagnet proximity effect is presented. 相似文献
4.
5.
The oscillation behavior of the superconducting transition temperature Tc as a function of the ferromagnetic Co layer thickness (dCo) has been examined for Nb/Co superconductor(S)/ferromagnetic(F) trilayer series (F/S/F) and pentalayer series (F/S/F/S/F). Tc of the pentalayer series takes a local maximum between dCo=2.0-3.2 nm, where Tc of the trilayer shows a local minimum. This difference in the Tc versus dCo curves provides a clear evidence for the occurrence of the pi phase in the pentalayers, which has been theoretically predicted by Buzdin et al., Radovic et al., and Tagirov. 相似文献
6.
E. G. Petrov 《JETP Letters》2018,107(5):302-306
The spin-valve effect in superconductor hybrid structures based on magnetic materials with a noncollinear magnetic ordering is described theoretically. It is shown that the following effect is possible in such structures: when the sample is magnetized, the critical temperature of the superconducting transition increases. The origin is the suppression of long-range triplet superconducting correlations. Such structures can be used as newtype memory elements for superconducting spintronics. 相似文献
7.
J. Kehrle V.I. Zdravkov G. Obermeier J. Garcia‐Garcia A. Ullrich C. Müller R. Morari A.S. Sidorenko S. Horn L.R. Tagirov R. Tidecks 《Annalen der Physik》2012,524(1):37-47
Ferromagnet/Superconductor/Ferromagnet (F/S/F) trilayers, in which the establishing of a Fulde‐Ferrell Larkin‐Ovchinnikov (FFLO) like state leads to interference effects of the superconducting pairing wave function, form the core of the superconducting spin valve. The realization of strong critical temperature oscillations in such trilayers, as a function of the ferromagnetic layer thicknesses or, even more efficient, reentrant superconductivity, are the key condition to obtain a large spin valve effect, i.e. a large shift in the critical temperature. Both phenomena have been realized experimentally in the Cu41Ni59/Nb/Cu41Ni59 trilayers investigated in the present work. 相似文献
8.
We analyze the proximity effect in a superconductor/ferromagnet (S/F) structure with a local inhomogeneity of the magnetization in the ferromagnet near the S/F interface. We demonstrate that not only the singlet but also the triplet component of the superconducting condensate is induced in the ferromagnet due to the proximity effect. The singlet component penetrates into the ferromagnet over a short length xi(h) = sqrt[D/h] ( h is the exchange field and D the diffusion coefficient), whereas the triplet component penetrates over a long length sqrt[D/epsilon] and leads to a significant increase of the ferromagnet conductance below the superconducting critical temperature Tc. 相似文献
9.
The proximity effect of a bulk superconductor (S) and a thin normal ferromagnetic metal layer (F) containing spin-orbit scattering centers is studied. The weak and strong limits of the proximity effect in the SF bilayer are considered analytically in the framework of the microscopic model of the superconducting state of dirty metals. The critical current of an SFIFS tunnel junction (I stands for an insulating layer) whose sides are made of proximity-coupled SF layers is calculated. Effects of spin-orbit scattering in the F layers on tunneling current are studied for parallel and antiparallel magnetization vectors of the F layers. It is shown that there is a complex relation between the magnitude of the superconducting current flowing through the SFIFS junction and scattering: spin-orbit scattering suppresses the exchange field effect in a nonlinear way and, at a fixed concentration of scattering centers, depends on the SF boundary resistance and the strength of the proximity effect. 相似文献
10.
In this paper we review some recent results obtained on superconducting/ferromagnetic (S/F) structures when measuring the dynamic instabilities of the vortex lattice at high driving currents. The role played on the non-equilibrium properties of the hybrids by both the ferromagnetic and the superconducting materials has been analyzed with a special focus on the values and the temperature dependence of the quasiparticle relaxation times, τ(E). Knowledge of the relaxation mechanisms in these systems is extremely important in view of possible applications since it can drive the optimal choice of both materials to realize, in particular, ultrafast superconducting single photon detectors based on S/F hybrid structures. 相似文献
11.
本文用对靶溅射技术制备了La2/3Ca1/3MnO3/YBa2Cu4O8/La2/3Ca1/3MnO3薄膜.与YBCO单层薄膜相比,由于超导/铁磁系统中的磁性邻近效应,三层薄膜表现出较低的超导转变温度.薄膜的R~T测量曲线显示出超磁阻(CMR)效应和超导转变,预示着超导和铁磁特性共存于LCMO/YBCO/LCMO三文治结构. 相似文献
12.
We have measured the nonlocal resistance of aluminum-iron spin-valve structures fabricated by e-beam lithography and shadow evaporation. The sample geometry consists of an aluminum bar with two or more ferromagnetic wires forming point contacts to the aluminum at varying distances from each other. In the normal state of aluminum, we observe a spin-valve signal which allows us to control the relative orientation of the magnetizations of the ferromagnetic contacts. In the superconducting state, at low temperatures and excitation voltages well below the gap, we observe a spin-dependent nonlocal resistance which decays on a smaller length scale than the normal-state spin-valve signal. The sign, magnitude, and decay length of this signal are consistent with predictions made for crossed Andreev reflection. 相似文献
13.
The magnetoresistance effects in the bi- and trilayer hybrid planar superconductor/ferromagnet (S/F) structures based on Py (permalloy) and Nb near the superconducting transition temperature T C are considered. It has been experimentally shown that the sign of the observed magnetoresistance peaks in the bilayer S/F systems changes from negative to positive at the permalloy layer thickness corresponding to the change in the type of domain walls from Néel to Bloch. For the Néel walls at the ferromagnet coercive fields, the negative magnetoresistance effect, which is due to a decrease in the depairing action of the exchange field E ex, is observed in the S/F bilayers. For the Bloch domain walls, the magnetoresistance of the bilayer S/F structures is determined by the dissipative motion of Abrikosov vortices in the superconducting layer. In the trilayer F/S/F structures, the magnetoresistance is mainly due to the suppression of the superconducting order parameter in the superconducting layer under the action of the accumulation of the spin-polarized carriers near the S/F interfaces. 相似文献
14.
Leksin PV Garif'yanov NN Garifullin IA Schumann J Kataev V Schmidt OG Büchner B 《Physical review letters》2011,106(6):067005
Superconductor-ferromagnet (S/F) spin valve effect theories based on the S/F proximity phenomenon assume that the superconducting transition temperature Tc of F1/F2/S or F1/S/F2 trilayers for parallel magnetizations of the F1 and F2 layers (T(c)(P)) are smaller than for the antiparallel orientations (T(c)(AP)). Here, we report for CoOx/Fe1/Cu/Fe2/In multilayers with varying Fe2-layer thickness the sign-changing oscillating behavior of the spin valve effect ΔT(c) = T(c)(AP) - T(c)(P). We observe the full direct effect with T(c)(AP) > T(c)(P) for Fe2-layer thickness d(Fe2) < 1 nm and the full inverse (T(c)(AP) < T(c((P)) effect for d(Fe2) ≥ 1 nm. Interference of Cooper pair wave functions reflected from both surfaces of the Fe2 layer appear as the most probable reason for the observed behavior of ΔT(c). 相似文献
15.
Using a method of free energy minimization, this paper investigates
the magnetization properties of a ferromagnetic (FM) monolayer and an
FM/antiferromagnetic (AFM) bilayer under a stress field,
respectively. It then investigates the magnetoresistance (MR) of
the spin-valve structure, which is built by an FM monolayer and an FM/AFM
bilayer, and its dependence upon the applied stress field.
The results show that under the stress field, the magnetization
properties of the FM monolayer is obviously different from that of the
FM/AFM bilayer, since the coupled AFM layer can obviously block the
magnetization of the FM layer. This phenomenon makes the MR of the
spin-valve structure become obvious. In detail, there are two
behaviors for the MR of the spin-valve structure dependence upon the
stress field distinguished by the coupling (FM coupling or AFM
coupling) between the FM layer and the FM/AFM bilayer. Either behavior of the MR
of the spin-valve structure depends on the stress field including
its value and orientation. Based on these investigations, a
perfect mechanical sensor at the nano-scale is suggested to be devised
experimentally. 相似文献
16.
H. Jirari R. Mélin N. Stefanakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):125-139
We consider the proximity effect in multiterminal ferromagnet/superconductor (FSF) hybrid structures in which two or three
electrodes are connected to a superconductor. We show that two competing effects take place in these systems: (i) pair breaking
effects due to the response to the exchange field induced in the superconductor; (ii) a reduction of the superconducting order
parameter at the interface that takes place already in NS junctions. We focus on this second effect that dominates if the
thickness of the S layer is small enough. We consider several single-channel electrodes connected to the same site. We calculate
the superconducting order parameter and the local density of state (LDOS). With two ferromagnetic electrodes connected to
a superconductor we find that the superconducting order parameter in the ferromagnetic alignment is larger than the superconducting
order parameter in the antiferromagnetic alignment ( > ), in agreement with [Eur. Phys. J. B 25, 373 (2002)]. If a third spin polarized electrode is connected to a superconductor we find that - can change sign as the transparency of the third electrode increases. This can be understood from the fact that the superconducting
order parameter is reduced if pair correlations among the ferromagnetic electrodes increase. If the two ferromagnetic electrodes
are within a finite distance we find Friedel oscillations in the Gorkov function but we still obtain > . 相似文献
17.
Cottet A 《Physical review letters》2011,107(17):177001
This work discusses theoretically the interplay between the superconducting and ferromagnetic proximity effects, in a diffusive normal metal strip in contact with a superconductor and a nonuniformly magnetized ferromagnetic insulator. The quasiparticle density of states of the normal metal shows clear qualitative signatures of triplet correlations with spin one (TCS1). When one goes away from the superconducting contact, TCS1 focus at zero energy under the form of a peak surrounded by dips, which show a typical spatial scaling behavior. This effect can coexist with a focusing of singlet correlations and triplet correlations with spin zero at finite but subgap energies. The simultaneous observation of both effects would enable an unambiguous characterization of TCS1. 相似文献
18.
O. V. Vikhrova Yu. A. Danilov Yu. N. Drozdov B. N. Zvonkov A. V. Kudrin V. V. Podol’skii M. V. Sapozhnikov 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(1):25-27
The magnetotransport properties of epitaxial ferromagnet/semiconductor heterostructures based on MnAs and GaMnAs ferromagnetic layers, separated by a nonmagnetic semiconductor layer (InAs or GaAs), have been investigated. Structures were obtained by combination of laser deposition and metal-organic chemical vapor deposition. A spin-valve effect was observed in magnetoresistance measurements. This fact suggests spin-polarized transport of carriers between ferromagnetic layers. 相似文献
19.
Westerholt K Sprungmann D Zabel H Brucas R Hjörvarsson B Tikhonov DA Garifullin IA 《Physical review letters》2005,95(9):097003
We studied superconducting V layers deposited on an antiferromagnetically coupled [Fe(2)V(11)](20) superlattice. The parallel upper critical magnetic field exhibits an anomalous T dependence up to the ferromagnetic saturation field of the superlattice, indicating that the superconducting transition temperature T(S) decreases when rotating the relative sublattice magnetization directions of the superlattice from antiparallel to parallel. This proves that the pair breaking effect of a Fe2 layer is reduced if at a distance of 1.5 nm a second Fe2 layer with antiparallel spin orientation exists. 相似文献
20.
G. A. Ovsyannikov A. E. Sheyerman A. V. Shadrin Yu. V. Kislinskii K. Y. Constantinian A. Kalabukhov 《JETP Letters》2013,97(3):145-148
The superconducting current induced by the penetration of the long-range triplet component of superconducting correlations into a composite ferromagnetic interlayer has been detected in mesa-heterostructures based on oxide cuprate superconductors YBa2Cu3O7 ? δ and Au/Nb bilayer films with the composite oxide interlayer that is made of ferromagnetic films of manganite La0.7Sr0.3MnO3 and ruthenate SrRuO3 and has a thickness much larger than the length of correlations determined by the exchange field. The deviation of the superconducting current in the mesa-heterostructure with the fraction of the second harmonic of 13% from a sinusoidal current-phase relation has been detected; this deviation can also be due to the generation of the triplet component of superconducting correlations in the ferromagnet. 相似文献