Magnetic proximity effect at the interface between a cuprate superconductor and an oxide spin valve

Ovsyannikov, G. A.; Демидов, В. В.; Khaydukov, Yu. N.; Mustafa, L.; Constantinian, K. Y.; Kalabukhov, A.; Winkler, Dag

doi:10.1134/s1063776116040063

Cited by 10 publications

(10 citation statements)

References 46 publications

(92 reference statements)

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“…Below T c we have observed an upturn of the magnetic moment if the sample was cooled down in certain magnetic field. A similar upturn, often called Paramagnetic Meissner Effect (PME) was already observed in several prior works [48,[52][53][54][55][56] and explained either by electrodynamical or exchange coupling mechanisms. Based on (a) the observation of the effect at high fields, (b) the linear field dependence of the enhanced moment and (c)the absence of the effect in PNR we attribute the PME in our samples to out-of-plane vortices.…”

Section: Discussionsupporting

confidence: 72%

Magnetic and superconducting phase diagram of Nb/Gd/Nb trilayers

et al. 2018

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We report on a study of the structural, magnetic and superconducting properties of Nb(25nm)/Gd(d f )/Nb(25nm) hybrid structures of a superconductor/ ferromagnet (S/F) type. The structural characterization of the samples, including careful determination of the layer thickness, was performed using neutron and X-ray scattering with the aid of depth sensitive mass-spectrometry. The magnetization of the samples was determined by SQUID magnetometry and polarized neutron reflectometry and the presence of magnetic ordering for all samples down to the thinnest Gd(0.8nm) layer was shown. The analysis of the neutron spin asymmetry allowed us to prove the absence of magnetically dead layers in junctions with Gd interlayer thickness larger than one monolayer. The measured dependence of the superconducting transition temperature Tc(d f ) has a damped oscillatory behavior with well defined positions of the minimum at d f =3nm and the following maximum at d f =4nm; the behavior, which is in qualitative agreement with the prior work (J.S. Jiang et al, PRB 54, 6119). The analysis of the Tc(d f ) dependence based on Usadel equations showed that the observed minimum at d f =3nm can be described by the so called "0" to "π" phase transition of highly transparent S/F interfaces with the superconducting correlation length ξ f ≈ 4nm in Gd. This penetration length is several times higher than for strong ferromagnets like Fe, Co or Ni, simplifying thus preparation of S/F structures with d f ∼ ξ f which are of topical interest in superconducting spintronics.

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Section: Discussionsupporting

confidence: 72%

Magnetic and superconducting phase diagram of Nb/Gd/Nb trilayers

et al. 2018

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“…Later, however, PME was observed in conventional superconductors, like Al or Nb, which required a less exotic explanation (see review [1] on the PME in bulk superconductors). One of such explanations is based on flux trapping below T C with further compression upon cooling [2,3].A similar effect, the increase of magnetic moment, was also observed recently in superconductor/ ferromagnet heterostructures (S/F) of different compositions [4][5][6][7][8][9][10] with both HTSC and conventional superconductors. For the explanation of the PME in S/F structures different models based on electrodynamical or exchange coupling mechanisms were proposed.…”

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confidence: 80%

“…In the former case the presence of the stray field produced by the F layer and the response of the superconductor to this field is usually considered [7][8][9]. The second model requires the presence of exchange coupled electrons on the S/F interface [4,5,10] due to the proximity effect. At the moment there is no unanimous opinion regarding the nature of the PME in S/F structures.…”

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confidence: 99%

On the explanation of the paramagnetic Meissner effect in superconductor/ferromagnet heterostructures

Nagy¹,

Khaydukov²,

Efremov³

et al. 2016

EPL

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-An increase of the magnetic moment in superconductor/ferromagnet (S/F) bilayers V(40nm)/F [F=Fe(1,3nm), Co(3nm), Ni(3nm)] was observed using SQUID magnetometry upon cooling below the superconducting transition temperature TC in magnetic fields of 10 Oe to 50 Oe applied parallel to the sample surface. A similar increase, often called the paramagnetic Meissner effect (PME), was observed before in various superconductors and superconductor/ferromagnet systems. To explain the PME effect in the presented S/F bilayers a model based on a row of vortices located at the S/F interface is proposed. According to the model the magnetic moment induced below TC consists of the paramagnetic contribution of the vortex cores and the diamagnetic contribution of the vortex-free region of the S layer. Since the thickness of the S layer is found to be 3-4 times less than the magnetic field penetration depth, this latter diamagnetic contribution is negligible. The model correctly accounts for the sign, the approximate magnitude and the field dependence of the paramagnetic and the Meissner contributions of the induced magnetic moment upon passing the superconducting transition of a ferromagnet/superconductor bilayer.The paramagnetic Meissner effect (PME), i.e. the appearance of a positive (rather than a negative) moment below the superconducting transition temperature T C was first observed in high-T C superconductors (HTSC) cooled in small fields (less than ∼ 5 Oe) and initially was explained by peculiarities of the d-wave electron coupling in those systems. Later, however, PME was observed in conventional superconductors, like Al or Nb, which required a less exotic explanation (see review [1] on the PME in bulk superconductors). One of such explanations is based on flux trapping below T C with further compression upon cooling [2,3].A similar effect, the increase of magnetic moment, was also observed recently in superconductor/ ferromagnet heterostructures (S/F) of different compositions [4][5][6][7][8][9][10] with both HTSC and conventional superconductors. For the explanation of the PME in S/F structures different models based on electrodynamical or exchange coupling mechanisms were proposed. In the former case the presence of the stray field produced by the F layer and the response of the superconductor to this field is usually considered [7][8][9]. The second model requires the presence of exchange coupled electrons on the S/F interface [4,5,10] due to the proximity effect. At the moment there is no unanimous opinion regarding the nature of the PME in S/F structures.p-1

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“…No wonder that this proximity effect is accompanied by the back-action of the ferromagnet on the superconducting subsystem revealing in the leakage of the magnetic moments and fields through the S/F interface. The resulting magnetic fields induced inside the superconductor have been experimentally observed with a variety of techniques including the nuclear magnetic resonance 4 , polar Kerr effect analysis 5 , neutron scattering 8,11,12 , and muon spin rotation measurements 6,7,13 .…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic proximity effect controlled by spin-triplet correlations in superconducting spin-valve structures

et al. 2019

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The spin-triplet correlations in superconducting spin valve structures arising in the presence of noncollinear textures of magnetic moment are shown to enhance strongly the electromagnetic proximity effect, i. e. the long-range leakage of the magnetic field from the ferromagnet (F) to the superconducting (S) layer. Both the dirty and clean limits are studied on the basis of the Usadel and Eilenberger theory, correspondingly. Our results suggest a natural explanation for the puzzling enhancement of the spontaneous magnetic fields induced by the noncollinear magnetic structures observed by the muon spin rotation techniques in a wide class of layered S/F systems. We show that the electromagnetic proximity effect causes the shift of the Fraunhofer dependence of the critical current on the external magnetic field in the Josephson junction with one superconducting electrode covered by the ferromagnetic layer. This provides an alternative way to measure both the magnitude and the direction of the spontaneous magnetic field induced in the superconductor. We also demonstrate the possibility of the long ranged superconductivity control of the magnetic state in F1/S/F2 structures.

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Magnetic proximity effect at the interface between a cuprate superconductor and an oxide spin valve

Cited by 10 publications

References 46 publications

Magnetic and superconducting phase diagram of Nb/Gd/Nb trilayers

Magnetic and superconducting phase diagram of Nb/Gd/Nb trilayers

On the explanation of the paramagnetic Meissner effect in superconductor/ferromagnet heterostructures

Electromagnetic proximity effect controlled by spin-triplet correlations in superconducting spin-valve structures

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