Shape of a magnetic resonance line in a thin film on the surface of anisotropic superconductor with irregularly distributed Abrikosov's vortices

The form of an electron paramagnetic resonance (EPR) in a thin paramagnetic film (λ/10, λ-London's depth of magnetic field penetration into superconductor) overlying the surface of an anisotropic superconductor is calculated taking into account the local magnetic field non-uniformity of an irregular Abrikosov's vortex lattice. It is shown that the form of EPR is noticeably varied with the degree of irregularity of the superconductor vortex lattice. It is suggested that an inclusion of this circumstance into consideration may essentially change the conclusions made on the lattice type and parameters of this superconductor, which are typically derived from the analysis of the EPR form. © Springer Science+Business Media, Inc. 2007

Shape of the nuclear magnetic resonance line in anisotropic superconductors with an irregular vortex lattice

The NMR line shape in type-II superconductors has been constructed with allowance for a change in the nonuniform magnetic field of an irregular vortex lattice near the surface of a superconductor. The NMR line shape is shown to change as a function of the irregularity of the vortex lattice rather that being simply broadened. This change is related to a lowering of the local symmetry of the irregular vortex lattice in the superconductor. This circumstance can substantially change the conclusions regarding the vortex-lattice type and the superconductor parameters that are usually drawn from the NMR line shape. © Pleiades Publishing, Inc., 2006

Peculiarities of pinning and microwave absorption hysteresis in thin superconducting films

The results of experimental and theoretical studies of the hysteretic microwave absorption (MWA) in the superconducting Bi2Sr 2CaCu2O8 thin films are presented. It has been found experimentally that the hysteresis loop manifests some unusual features such as the non-monotone hysteresis variation and the change of a hysteresis sign. We have shown that such unusual behavior is due to the special nature of the bulk pinning in a superconducting film with a thickness comparable with the field penetration depth. The theoretical model of the MWA hysteresis has been developed taking into account the inhomogeneous distribution of centers with different symmetry of a pinning potential and their variation with the magnetic field value. © Springer Science+Business Media, LLC 2006

NMR lineshape in anisotropic superconductors

It is shown that the NMR lineshape strongly differs for various angles between normal to the surface of the superconductor and the external magnetic field direction. Thus, the surface effects drastically change the conclusions concerning the vortex lattice and parameters of the superconductor that are usually extracted from the NMR line shape. The NMR probing in the inclined magnetic fields will provide more detailed information about the parameters of the superconductor, especially in strongly anisotropic high-Tc. superconductors. © 2000 Elsevier Science B.V. All rights reserved

Inhomogeneous current distribution in a bimetal ferromagnet/superconductor film in a longitudinal magnetic field

The proximity effect of the ferromagnetic metal/superconductor (FM/S) bilayers in a 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 an 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

Critical temperature of a ferromagnet/superconductor structures in a parallel magnetic field

Two- and three-layered structures consisting of ferromagnetic metal (F) film and superconductor (S) film are considered in the magnetic field H applied parallel to the plane of the F/S interface. Magnetic-penetration depth is presumed much greater than thicknesses of layers. Assuming that both S and F layers are dirty the boundary problem for the Usadel function is solved taking account of so called "Umklapp processes" for momenta of superconducting pairs on the F/S interface. It is shown that the field H can significantly alter a functional form of the dependence of critical temperature Tc versus thickness of the F layer df. Keeping in mind the possible applications like the superonducting spin-valve the behavior of T c(df) for the F/S/F trilayer in the magnetic field is investigated. © 2009 IOP Publishing Ltd

Proximity effect for asymmetrical three-layered F/S structures in external magnetic field

We study the critical temperature T c of the three-layered ferromagnet/superconductor (F/S) structures in the external magnetic field H parallel to the film. For the F1/S/F2 and F1/F2/S asymmetrical trilayers, the triplet superconducting component is generated at noncollinear magnetizations of the F layers. Assuming that all S and F layers are dirty, we solve boundary problem for the Usadel function. The results of numerical calculations for T c as function thicknesses both F1 and F2 layers at various parameters F/S structure are presented. The application to the spin-switch problem is discussed. We found that asymmetry can essentially change the spin-switch observation condition. The re-entrant superconductivity caused by external magnetic field is predicted for the F1/F2/S trilayer. © 2013 The Korean Physical Society

Proximity effect for asymmetrical three-layered FS structures in external magnetic field

We study asymmetrical three-layers F1F2S and F 1SF2 structures in an external parallel magnetic field. Assuming that all F and S layers are dirty, we solve the boundary value problem for the Usadel function. We calculate the critical temperature of in F 1F2S and F1SF2 systems as function of the F layers thicknesses and external magnetic field. © (2012) Trans Tech Publications

Proximity effect for asymmetrical three-layered FS structures in external magnetic field

We study asymmetrical three-layers F1F2S and F 1SF2 structures in an external parallel magnetic field. Assuming that all F and S layers are dirty, we solve the boundary value problem for the Usadel function. We calculate the critical temperature of in F 1F2S and F1SF2 systems as function of the F layers thicknesses and external magnetic field. © (2012) Trans Tech Publications

Effect of a magnetic field on the critical temperature of a ferromagnet - Superconductor transition in layered heterostructures

Effect of an external magnetic field H on the superconductivity of bilayer (FS) and trilayer (FSF) heterostructures consisting of layers of ferromagnetic (F) and superconducting (S) metals has been studied. The case has been considered where the scattering in both metals is sufficiently strong (the so-called "dirty limit"), which makes it possible to use the Usadel equations to describe the proximity effect. For the Gor'kov function, a boundary problem is formulated that is free of restrictions on the magnitudes of the transparency of the FS (SF) interface and takes into account both the wave and diffusional types of motion of quasi-particles. Special attention is given to the case of a trilayer system, for which a detailed analysis of two states with parallel (P) and antiparallel (AP) directions of the magnetizations in the F layers has been performed. Based on the results obtained, the possibility of a technical application of the FSF system is considered. © Pleiades Publishing, Ltd., 2011