Extinction and Recovery of Superconductivity by Interference in Superconductor/Ferromagnet Bilayers

Сидоренко, А. С.; Zdravkov, V. I.; Kehrle, J.; Morari, R.; Antropov, E.; Obermeier, G.; Gsell, S.; Schreck, M.; Müller, Claus; Ryazanov, V. V.; Horn, S.; Tidecks, R.; Тагиров, Л. Р.

doi:10.1007/978-3-642-00708-8_1

Cited by 7 publications

(12 citation statements)

References 27 publications

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“…The resulting state has common origin with the famous LOFF-state 3,4 and can be reffered to as its mesoscopic analogue. This mesoscopic LOFF-state was predicted theoretically 5,6 and observed experimentally [7][8][9][10][11] . In this state Cooper pair acquires the total momentum 2Q or −2Q inside the ferromagnet as a response to the energy difference between the two spin directions.…”

Section: Introductionsupporting

confidence: 64%

Influence of spin-dependent quasiparticle distribution on the Josephson current through a ferromagnetic weak link

Bobkov

Bobkova

2011

Phys. Rev. B

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The Josephson current flowing through weak links containing ferromagnetic elements is studied theoretically under the condition that the quasiparticle distribution over energy states in the interlayer is spin-dependent. It is shown that the interplay between the spin-dependent quasiparticle distribution and the triplet superconducting correlations induced by the proximity effect between the superconducting leads and ferromagnetic elements of the interlayer, leads to the appearence of an additional contribution to the Josephson current. This additional contribution jt can be extracted from the full Josephson current in experiment. The features of the additional supercurrent jt, which are of main physical interest are the following: (i) We propose the experimental setup, where the contributions given by the short-range (SRTC) and long-range (LRTC) components of triplet superconducting correlations in the interlayer can be measured separately. It can be realized on the basis of S/N/F/N/S junction, where the interlayer is composed of two normal metal regions with a spiral ferromagnet layer sandwiched between them. For the case of tunnel junctions the measurement of jt in such a system can provide direct information about the energy-resolved anomalous Green's function components describing SRTC and LRTC. (ii) In some cases the exchange field-suppressed supercurrent can be not only recovered but also enhanced with respect to its value for non-magnetic junction with the same interface resistances by the presence of spin-dependent quasiparticle distribution. This effect is demonstrated for S/N/S junction with magnetic S/N interfaces. In addition, it is also found that under the considered conditions the dependence of the Josephson current on temperature can be nontrivial: at first the current rises upon temperature increasing and only after that starts to decline.

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Section: Introductionsupporting

confidence: 64%

Influence of spin-dependent quasiparticle distribution on the Josephson current through a ferromagnetic weak link

Bobkov

Bobkova

2011

Phys. Rev. B

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“…So far, our experimental data on S/F bilayers (with F = Cu 41 Ni 59 alloy) were fitted by theoretical curves, using a value for ξ S of about 10 nm (see Refs. [24] and [55,56] for T c (d F ) dependencies of sample series S15, S16 and of S21, S22, S23, respectively, and Refs. decreasing Nb layer thickness.…”

Section: Analysis Of the Data And Discussionmentioning

confidence: 99%

“…56,57] for T c (d S ) curves), instead of the improved value in the range of ξ S = 6.2-6.7 nm obtained from critical field measurements (see Sec. III B).…”

mentioning

confidence: 99%

Reentrant superconductivity in superconductor/ferromagnetic-alloy bilayers

et al. 2010

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We studied the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) like state established due to the proximity effect in superconducting Nb/Cu 41 Ni 59 bilayers. Using a special wedge-type deposition technique, series of 20-35 samples could be fabricated by magnetron sputtering during one run. The layer thickness of only a few nanometers, the composition of the alloy, and the quality of interfaces were controlled by Rutherford backscattering spectrometry, high resolution transmission electron microscopy, and Auger spectroscopy. The magnetic properties of the ferromagnetic alloy layer were characterized with superconducting quantum interference device (SQUID) magnetometry. These studies yield precise information about the thickness, and demonstrate the homogeneity of the alloy composition and magnetic properties along the sample series. The dependencies of the critical temperature on the Nb and Cu 41 Ni 59 layer thickness, T c (d S ) and T c (d F ), were investigated for constant thickness d F of the magnetic alloy layer and d S of the superconducting layer, respectively. All types of non-monotonic behaviors of T c versus d F predicted by the theory could be realized experimentally: from reentrant superconducting behavior with a broad extinction region to a slight suppression of superconductivity with a shallow minimum. Even a double extinction of superconductivity was observed, giving evidence for the multiple reentrant behavior predicted by theory. All critical temperature curves were fitted with suitable sets of parameters. Then, T c (d F ) diagrams of a hypothetical F/S/F spin-switch core structure were calculated using these parameters. Finally, superconducting spin-switch fabrication issues are discussed in detail in view of the achieved results.

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“…To provide superior homogeneity of the Si and Nb film thickness over the size of the substrate the "spray" deposition technique was employed [44,45]. To realize this technique a magnetron was moved along the substrate by a custom motorized setup providing a uniform coverage of the substrate surface with the sputtered material.…”

Section: Thin Film Deposition and Sample Preparationmentioning

confidence: 99%

Experimental and theoretical analysis of the upper critical field in ferromagnet–superconductor–ferromagnet trilayers

Antropov¹,

Kalenkov²,

Kehrle³

et al. 2013

Supercond. Sci. Technol.

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Abstract. The upper critical magnetic field H c2 in thin-film FSF trilayer spinvalve cores is studied experimentally and theoretically in geometries perpendicular and parallel to the heterostructure surface. The series of samples with variable thicknesses d F1 of the bottom and d F2 of the top Cu 41 Ni 59 F-layers are prepared in a single run, utilizing a wedge deposition technique. The critical field H c2 is measured in the temperature range 0.4 − 8 K and for magnetic fields up to 9 Tesla. A transition from oscillatory to reentrant behavior of the superconducting transition temperature versus F-layers thickness, induced by an external magnetic field, has been observed for the first time. In order to properly interpret the experimental data, we develop a quasiclassical theory, enabling one to evaluate the temperature dependence of the critical field and the superconducting transition temperature for an arbitrary set of the system parameters. A fairly good agreement between our experimental data and theoretical predictions is demonstrated for all samples, using a single set of fit parameters. This confirms adequacy of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) physics in determining the unusual superconducting properties of the studied Cu 41 Ni 59 /Nb/Cu 41 Ni 59 spin-valve core trilayers.Experimental and theoretical analysis of the upper critical field in FSF trilayers 2

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Extinction and Recovery of Superconductivity by Interference in Superconductor/Ferromagnet Bilayers

Cited by 7 publications

References 27 publications

Influence of spin-dependent quasiparticle distribution on the Josephson current through a ferromagnetic weak link

Influence of spin-dependent quasiparticle distribution on the Josephson current through a ferromagnetic weak link

Reentrant superconductivity in superconductor/ferromagnetic-alloy bilayers

Experimental and theoretical analysis of the upper critical field in ferromagnet–superconductor–ferromagnet trilayers

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