Lambert formula - Bouguer absorption law?

It is shown that the fundamental Bouguer law, which links the fraction of absorbed light to the intensity of the incident light for a constant thickness of absorbing layer, was discovered experimentally and that the Lambert law is in no way related to it. The Lambert formula can be used only to estimate the attenuation (transmission) of light in a homogeneous medium containing scattering heterogeneous particles and with no jumps of the refractive index. The fraction of light absorbed in a layer is shown to depend on the thickness of that layer. © 1998 Plenum Publishing Corporation

RKKY indirect exchange in low-dimensional superconductors

The indirect exchange interaction between localized moments (LMs), mediated by one- and two-dimensional superconducting electron gas, is calculated by means of thermodynamic Green functions. The interaction potential is expressed in terms of higher transcendental functions of distance R between LMs. The asymptotic behavior at large R is presented for 1D and 2D cases. It is shown that an additional long range potential appears in the superconducting state as compared with the normal one. © 1993

Exchange narrowing of dipolar broadened epr lines in superconductors

The exchange narrowing of dipolar broadened paramagnetic resonance (EPR) lines by the long range exchange interaction is considered. That is the actual situation. in magnetically diluted superconducting alloys, where a sharp decrease of the EPR linewidth under the superconducting transition was observed. These calculations show that the EPR linewidth drop below the superconducting transition temperature is a clear indication of the long wave-length electronic susceptibility decreasing in the superconducting state. © 1987 IEE

Proximity effect and superconducting transition temperature in superconductor/ferromagnet sandwiches

The theory of proximity effect for superconductor/ferromagnet (SC/FM) sandwiches is developed. The superconducting transition temperature Tc of a sandwich is calculated taking into account the finite transparency of the SC/FM interface, the exchange splitting of conduction band and breaking of superconducting pairs in the ferromagnetic layer(s). It is found that in SC/FM bilayers and FM/SC/FM trilayers Tc may exhibit nonmonotonic, oscillating or re-entrant behavior as a function of the ferromagnetic layer(s) thickness. The qualitative relevance of the theory to existing experiments is discussed. The experiment which allows one to distinguish the formation of 'π-phase' or '0-phase' in SC/FM multilayer systems is proposed. © 1998 Elsevier Science B.V. All rights reserved

Huge magnetoresistance in magnetic nanocontacts

The quasiclassical theory of a nanosize point contacts (PC) between two ferromagnets is developed. The maximum available magnetoresistance in PC is calculated for ballistic and diffusive transport at the area of a contact, in the ballistic regime, the magnetoresistance in excess of few hundreds percents is obtained for the iron-group ferromagnets. The regime of quantized conductance through the magnetic nanocontact is considered. It is shown that magnetoresistance is tremendously enhanced at small number of open conductance channels. The quantum spin valve realization is discussed in detail, and recent observations of huge (up to 100 000 %) magnetoresistance in the electrodeposited nickel nanocontacts are discussed in the framework of the developed theory

Low-field superconducting spin switch based on a superconductor/ferromagnet multilayer

The principle of a novel device, called a superconducting spin switch or a spin valve for supercurrent, based on a four-layer antiferromagnet/ferromagnet/superconductor/ferromagnet spin-valve-like structure was investigated. Results show that the parallel alignment of magnetizations in the ferromagnetic layer of this structure has either zero value or lower superconducting transition temperature compared to an antiparallel alignment of magnetizations. Thus, the rotation of magnetization of the top free ferromagnetic layer by a weak external magnetic field can switch the supercurrent flowing through the superconducting layer

Critical temperature of superconductor/ferromagnet bilayers

Superconductor/ferromagnet bilayers are known to exhibit nontrivial dependence of the critical temperature T_c on the thickness d_f of the ferromagnetic layer. We develop a general method for investigation of T_c as a function of the bilayer's parameters. It is shown that interference of quasiparticles makes T_c(d_f) a nonmonotonic function. The results are in good agreement with experiment. Our method also applies to multilayered structures.Comment: 4 pages, 2 EPS figures; the style file jetpl.cls is included. Version 2: typos correcte

Thermodynamic properties of ferromagnetic/superconductor/ferromagnetic nanostructures

The theoretical description of the thermodynamic properties of ferromagnetic/superconductor/ferromagnetic (F/S/F) systems of nanoscopic scale is proposed. Their superconducting characteristics strongly depend on the mutual orientation of the ferromagnetic layers. In addition, depending on the transparency of S/F interfaces, the superconducting critical temperature can exhibit four different types of dependences on the thickness of the F-layer. The obtained results permit to give some practical recommendations for the spin-valve effect experimental observation. In this spin-valve sandwich, we also expect a spontaneous transition from parallel to anti-parallel ferromagnetic moment orientation, due to the gain in the superconducting condensation energy.Comment: 20 pages, 5 figures, submitted to PR