Superconducting Probe of Electronic Correlations and Exchange Field Based on the Proximity Effect in F/S Nanostructures

The proximity effect and competition between the BCS and LOFF states are studied in the Cooper limit for thin F/S and F/S/F nanostructures, where F is a ferromagnet and S is a superconductor. The dependences of the critical temperature Tc on the exchange field I, electron correlations λf, and the thickness df of the F layer are derived for F/S bilayers and F/S/F trilayers. Two new π-phase superconducting states with electronelectron repulsion in the F layers of F/S/F trilayers are predicted. A 2D LOFF state in F/S/F trilayers is possible only in the presence of a weak magnetic field and the appropriate parameters of the F and S layers. The absence of the suppression of 3D superconductivity in short-period Gd/La superlattices is explained and the electronelectron coupling constant in gadolinium is predicted. A method of superconducting probe spectroscopy based on the proximity effect is proposed for determining the symmetry of the order parameter, the magnitude and sign of electron correlations, and the exchange field in various nanomagnets F.

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Proximity Effect as a Probe of Electronic Correlations and Exchange Field in Dirty Ferromagnet/Superconductor Nanostructures

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.152-153.457 ◽

2009 ◽

Vol 152-153 ◽

pp. 457-461

Author(s):

Larisa A. Terentieva ◽

Elena L. Parfenova ◽

Mansur G. Khusainov ◽

Yurii N. Proshin

Keyword(s):

Magnetic Field ◽

Critical Temperature ◽

Proximity Effect ◽

Order Parameter ◽

Weak Magnetic Field ◽

Exchange Field ◽

Electronic Correlations ◽

Electron Repulsion ◽

Parameter Symmetry ◽

Order Parameter Symmetry

We investigate the interplay between the BCS and 2D Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) states in the dirty thin ferromagnetic metal/superconductor (FM/S) nanostructures. For the FM/S bilayers we have derived the dependencies of critical temperature on the FM layer exchange field, electronic correlations and thickness. Moreover, in the corresponding FM/S/FM trilayers we predict two new π phase superconducting states with electron-electron repulsion in the FM layers. The 2D modulated LOFF states are possible in such trilayers only in presence of a weak magnetic field and at suitable parameters of the FM and S layers. On this base we originally propose the method of proximity effect probe the magnitude and sign of the electronic correlations, the order parameter symmetry and exchange fields in various FM layers.

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Inhomogeneous Current Distribution in a Bimetal Ferromagnet/Superconductor Film in a Longitudinal Magnetic Field

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.152-153.462 ◽

2009 ◽

Vol 152-153 ◽

pp. 462-465 ◽

Cited By ~ 3

Author(s):

Maxim Avdeev ◽

Mansur G. Khusainov ◽

Yurii N. Proshin ◽

Sergey Tsarevskii

Keyword(s):

Magnetic Field ◽

Critical Temperature ◽

Current Distribution ◽

Proximity Effect ◽

Longitudinal Magnetic Field ◽

Dirty Limit ◽

Distribution Versus ◽

Superconductor Film ◽

Interface Transparency ◽

Superconducting Current

The proximity effect of the ferromagnetic metal/superconductor (FM/S) bilayers in а external longitudinal magnetic field is considered in the dirty limit. The critical temperature and the superconducting current distribution versus applied magnetic field’s magnitude, film’s thicknesses and a transparency of the contact is calculated, with taking into account аn umklapp processes possibility on the interface of the FM/S contact. It is shown that superconducting current is strictly inhomogeneous and asymmetrical. It is shown also that the current inhomogeneity depends heavily from the FM/S interface transparency.

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TRANSPORT AND TRIPLET SUPERCONDUCTING CONDENSATE IN MESOSCOPIC FERROMAGNET-SUPERCONDUCTOR STRUCTURES

International Journal of Modern Physics B ◽

10.1142/s0217979202010312 ◽

2002 ◽

Vol 16 (10) ◽

pp. 1459-1478 ◽

Cited By ~ 2

Author(s):

F. S. BERGERET ◽

V. V. PAVLOVSKII ◽

A. F. VOLKOV ◽

K. B. EFETOV

Keyword(s):

Critical Temperature ◽

Normal State ◽

Proximity Effect ◽

Exchange Field ◽

Local Inhomogeneity ◽

Dirty Limit ◽

Mesoscopic Structure ◽

Superconducting Condensate

We calculate the conductance of a superconductor/ferromagnet (S/F) mesoscopic structure in the dirty limit. First we assume that the ferromagnet exhibits a homogeneous magnetization and consider the case that the penetration of the condensate into the F wire is negligible and the case in which the proximity effect is taken into account. It is shown that if the exchange field is large enough, the conductance below the critical temperature T c , is always smaller than the conductance in the normal state. At last, we calculate the conductance for a F/S structure with a local inhomogeneity of the magnetization in the ferromagnet. We demonstrate that a triplet component of the condensate is induced in the F wire. This leads to a increase of the conductance below T c .

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Proximity Effect for Asymmetrical Three-Layered FS Structures in External Magnetic Field

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.190.387 ◽

2012 ◽

Vol 190 ◽

pp. 387-390

Author(s):

Maxim Avdeev ◽

Yurii N. Proshin ◽

Mansur G. Khusainov ◽

Sergey Tsarevskii

Keyword(s):

Magnetic Field ◽

Critical Temperature ◽

External Magnetic Field ◽

Boundary Value Problem ◽

Proximity Effect ◽

Boundary Value ◽

Netic Field

We study asymmetrical three-layers F1F2S and F1SF2 structures in an external parallelmag-netic field. Assuming that all F and S layers are dirty, we solve the boundary value problem for theUsadel function. We calculate the critical temperature of in the F1F2S and F1SF2 systems as functionof the F layers thicknesses and external magnetic field.

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Weak magnetic field effects on chiral critical temperature in a nonlocal Nambu–Jona-Lasinio model

International Journal of Modern Physics A ◽

10.1142/s0217751x15501237 ◽

2015 ◽

Vol 30 (21) ◽

pp. 1550123 ◽

Cited By ~ 5

Author(s):

M. Loewe ◽

F. Marquez ◽

C. Villavicencio ◽

R. Zamora

Keyword(s):

Magnetic Field ◽

Critical Temperature ◽

Temperature Effects ◽

Weak Magnetic Field ◽

Chiral Limit ◽

Homogeneous Magnetic Field ◽

Magnetic Field Effects ◽

Chiral Symmetry Restoration ◽

Nonlocal Models ◽

Low Magnetic Field

In this paper we study the nonlocal Nambu–Jona-Lasinio model with a Gaussian regulator in the chiral limit. Finite temperature effects and the presence of a homogeneous magnetic field are considered. The magnetic evolution of the critical temperature for chiral symmetry restoration is then obtained. Here, we restrict ourselves to the case of low magnetic field values, being this a complementary discussion to the existing analysis in nonlocal models in the strong magnetic field regime.

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Proximity effect enhancement induced by a superconducting anti-dot

Modern Physics Letters B ◽

10.1142/s021798491450242x ◽

2014 ◽

Vol 28 (31) ◽

pp. 1450242

Author(s):

Sindy J. Higuera ◽

Miryam R. Joya ◽

J. Barba-Ortega

Keyword(s):

Magnetic Field ◽

External Magnetic Field ◽

Proximity Effect ◽

Magnetization Curve ◽

Order Parameter ◽

Proximity Effects ◽

Time Dependent ◽

Critical Fields ◽

Ginzburg Landau ◽

Ginzburg Landau Equations

In this work, we study the proximity and pinning effects of a rectangular superconducting anti-dot on the magnetization curve of a mesoscopic sample. We solve the nonlinear time-dependent Ginzburg–Landau equations for a superconducting rectangle in the presence of a magnetic field applied perpendicular to its surface. The pinning effects are determined by the number of vortices into the anti-dot. We calculate the order parameter, vorticity, magnetization and critical fields as a function of the external magnetic field. We found that the size and nature of the anti-dot strongly affect the magnetization of the sample. The results are discussed in framework of pinning and proximity effects in mesoscopic systems.

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π Phase Superconductivity and Magnetism in Ferromagnet / Superconductor / Ferromagnet Trilayers

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.152-153.512 ◽

2009 ◽

Vol 152-153 ◽

pp. 512-517

Author(s):

Mansur G. Khusainov ◽

Yurii N. Proshin

Keyword(s):

Magnetic Field ◽

External Magnetic Field ◽

Boundary Value Problem ◽

Total Momentum ◽

Electron Interaction ◽

Exchange Field ◽

Two Phase ◽

High Tc ◽

Short Period ◽

Magnetic States

On the base of new boundary-value problem for the Eilenberger function we investigate the superconducting and magnetic states in ferromagnet/superconductor (FM/S) nanostructures, where superconductivity is a superposition of the BCS pairing with zero total momentum in the S layers and the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing with nonzero 3D coherent momentum k in the FM layers. We originally study the interplay between the BCS and FFLO states in the pure thin FM/S/FM trilayers and two novel -phase superconducting states with electron-electron repulsion in the FM layers are predicted. The modulated FFLO states are possible in such trilayers only in presence of external magnetic field at suitable parameters of the FM and S layers. In the FM/S superlattices there are also two -phase magnetic states (0 and ) with compensation of the exchange field paramagnetic effect. This fact allows us to explain a surprisingly high Tc ~ 5K in the short period Gd/La superlattice and to predict the sign and value of the electron-electron interaction in the ferromagnetic Gd metal.

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The Josephson Current in the SFS Sandwich Taking into Account the Proximity Effect and Umklapp Processes

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.190.425 ◽

2012 ◽

Vol 190 ◽

pp. 425-428

Author(s):

Vadim A. Tumanov ◽

Yurii N. Proshin

Keyword(s):

Experimental Data ◽

Critical Temperature ◽

Temperature Dependence ◽

Proximity Effect ◽

Order Parameter ◽

Josephson Effect ◽

Josephson Current ◽

Internal Boundary ◽

Effect Theory ◽

Good Agreement

We consider the Josephson effect in a three-layer symmetric superconductor-ferromagnet-superconductor (SFS) system. In the framework of the proximity effect theory we calculate the Josephson current as a function of the ferromagnet thickness, taking into account the Umklapp processes at the internal boundary and the critical temperature dependence of the order parameter phase difference. The results of the calculations are in good agreement with experimental data.

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