Table of contents

The review examines the dynamics of a special class of magnetic substances (magnetically ordered crystals) in which the magnetic atoms do not coincide with the symmetry center (provided that such a center exists in the crystal). Research into the magnetoelectric and antiferroelectric interactions in such magnets has led to a new section in the spin dynamics of both the electrical and nuclear subsystems. The review is based primarily on the latest works (2001 – 2004) done by theoretical physicists from the Ural region. Several results of the pioneering works (1988 – 1990) of Ukrainian physicists, who opened this new section in spin dynamics, are also discussed. All this research has made it possible to compare the predicted effects for different crystal systems and thus has provided a more meaningful arrangement of the desired experiments.

Astronomical observations of recent years have substantially extended our knowledge of the rotation of stars. Helioseismology has found out that the equator-to-pole decline in the angular velocity observed on the solar surface traces down to the deep interior of the Sun. New information has been gained regarding the dependence of the rotational nonuniformities on the angular velocity and mass of the star. These achievements have prompted the development of the theory of differential rotation, which is the focal point of this review. Nonuniform rotation results from the interaction of turbulent convection with rotation. The investigation into the turbulent mechanisms of angular-momentum transport has reached a level at which the obtained results can serve as the basis for developing quantitative models of stellar rotation. Such models contain virtually no free parameters but closely reproduce the helioseismological data on the internal rotation of the Sun. The theoretical predictions on the differential rotation of the stars agree with observations. A brief discussion is held here on the relation between the magnetic activity of stars and the nonuniformity of their rotation and on prospects for further development of the theory.

The nature of photocounts arising in detectors exposed to highly coherent laser radiation is discussed. It is shown that the spatial localization of a photon allowed in quantum electrodynamics fails to account for the effect observed and that the Coulomb instability of a low electron flux in a photodetector can be the explanation. With detectors utilizing non-free electrons, namely, electrons bound in atoms, ions, molecules, etc., weak optical signals can be detected with laser radiation without photocounts, in other words, at a suppressed shot noise. A basic scheme for a laser detector using bound electrons is suggested.

The review is concerned with the current status of research on the use of plasma jets for the modification of surface properties of metalware, as well as of investigations of doping and mass transfer of elements. The effect of thermal plasma parameters on the efficiency of surface processing of metal materials is discussed. The structure and properties of protective coatings produced by exposure to pulsed plasmas are analyzed. A new direction for the production of combined coatings is considered. Their structure and properties were studied by the example of Fe, Cu, steels, and alloys, including titanium alloys; the modification process was shown to be controllable by the action of pulsed plasma jets. The physical factors that affect the modification process and the coating deposition, and their effect on the structure and properties of metallic, ceramic – metal, and ceramic coatings were analyzed.

The Majorana formula for the probability of spin-flipping in a time-dependent magnetic field which almost vanishes at a certain moment is discussed in connection with the celebrated work by Landau, Zener, and Stückelberg for nonadiabatic dynamics in the avoided crossing situation.