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

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

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

Boundary conditions for quasiclassical Green functions at superconductor-ferromagnet interface

The quasiclassical equations of superconductivity for a metal with spin-split conduction band are derived. The boundary conditions for the Green functions at the interface between a ferromagnet and a superconductor are obtained. They are valid for the arbitrary magnitude of exchange splitting of a ferromagnet conduction band. © 2000 Elsevier Science B.V. All rights reserved

Spin-flip and domain wall magnetoresistance in quantum magnetic nanocontacts

The theory of nanosize point contacts made of ferromagnetic metals is developed. A general quantum scattering theory is applied to calculate magnetoresistance of a nanocontact with a domain wall located in the constriction. The exact solution of the electron motion in a potential of the linear domain wall is used as a zero-order approximation. Spin-flip and spin-conserving quantized conductances of the nanocontact are calculated by the perturbation theory by the difference between the model and the Cabrera-Falicov potentials of the domain wall. It is explicitly shown that spin-flip conductance imposes natural limitation on magnetoresistance of the point contact, which otherwise diverges in the regime of complete spin-rectified conductance through the contact. © 2009 Elsevier B.V. All rights reserved

Boundary resistance in magnetic multilayers

Quasiclassical boundary conditions for electrochemical potentials at the interface between diffusive ferromagnetic and non-magnetic metals are derived for the first time. An expression for the boundary resistance accurately accounts for the law of conservation of momentum as well as essential gradients of the chemical potentials. Conditions are established at which spin asymmetry of the boundary resistance has a positive or negative sign. Dependence of the spin asymmetry and the absolute value of the boundary resistance on the exchange splitting of the conduction band opens up new possibilities for estimating spin polarization of the conduction band of ferromagnetic metals. Consistency of the theory is checked on existing experimental data. © 2006 IOP Publishing Ltd

Spin kinetics and EPR in superconductors

The theory of the electron paramagnetic resonance (EPR) on magnetic impurities in type-II superconductors is presented. The kinetic equations describing the coupled motion of the magnetisation of localised spins and that of conduction electrons' spins are derived and solved. Analytical expressions for the relaxation rates, being the real parts of kinetic coefficients entering the equations, are obtained. These expressions are valid at arbitrary temperatures and frequencies of resonance within the approximation of the homogeneous superconductor. The detailed numerical analysis, allowing the authors to plot the temperature dependence of the EPR linewidth, is carried out. It is shown that the 'electronic bottleneck effect' becomes stronger in the superconducting state and, as a result, the linewidth becomes a monotonic function of temperature. The EPR experiments on superconducting systems are discussed