Yurii A. Izyumov

THEORY OF SCATTERING OF SLOW NEUTRONS IN MAGNETIC CRYSTALS

When considering the scattering of slow neutrons in matter under conditions remote from those of resonance capture by atomic nuclei, one usually starts from the Born approximation, corresponding to the first order of perturbation theory. In a case in which the scattering material consists of a large number of particles (for example, a crystal), it is convenient to introduce a time formalism into the theory in order to calculate the scattering cross sections. In its most general presentation, the problem takes the following form.

Origin of nonmonotonic Tc behavior in ferromagnet/superconductor structures

Abstract The original theory of proximity effect in the layered ferromagnetic metal/superconductor (FM/S) structures taking into account a finite transparency of FM/S interface as well as a competition between 1D and 3D Larkin–Ovchinnikov–Fulde–Ferrell (LOFF) states is developed. It is shown that the oscillatory dependence of critical temperature Tc on the FM layer thickness df is due to oscillations of the Cooper pairs flux at the FM/S boundary. This effect is possible not only in the FM/S multilayers, but in the FM/S bilayers as well. The phenomena of reentrant and periodically reentrant superconductivity in the FM/S bilayers and superlattices are predicted. The competition between 1D and 3D LOFF states leads to significant smoothing of the Tc(df) dependence, so that in the most cases one maximum of this dependence is realized as this has been observed in Gd/Nb and Fe/Nb/Fe.