Table of contents

Theoretical and experimental work on the effect of light on the magnetic properties of strongly magnetic materials is reviewed. This phenomenon is caused primarily by the change in the exchange interaction and magnetic anisotropy. The manifestations of photomagnetism are very diverse. Light can affect the long-range order, raising the Curie point of ferromagnetic materials, changing the type of ordering or giving rise to the appearance of magnetization in antiferromagnetic materials. Light can also change the domain structure, affect the motion of domain walls under the action of external forces, and itself give rise to the motion of domain walls. From the theoretical viewpoint, photoinduced order-disorder phase transitions are of special interest as an example of phase transitions in open systems. The review covers works published up to September 1985.

The fundamental mechanisms of a metal-dielectric transition are examined. The multiband theory of the metal-dielectric transition is reviewed, as based on realistic models of the band structure of a set of oxides and sulfides of the 3d-metals in which the transition is accompanied by structural and magnetic phase transitions. In the multiband case new phases arise that were absent in the simplest single-band theories, yet at the same time are known experimentally. The metal-dielectric transition is studied in the Shubin-Vonsovskiĭ model. It is shown that allowance for screening of the long-range Coulomb interaction leads to a first-order transition. We describe the concept of the metallic order parameter, which is proportional near the transition point to the density of states at the Fermi level. The theory enables one to explain qualitatively many experimental data, mainly thermodynamic, on the oxides of vanadium and titanium and the sulfides of 3d-metals having a metal-dielectric transition. The pathways are discussed of further development of the theory for fuller description of all physical properties of the materials being studied. Cases are analyzed in which localized magnetic moments exist and are manifested alongside the band states.

The MHD theory of the equilibrium and stability of the plasma in a stellarator is set forth. Various ways to develop magnetic configurations of the stellarator type are examined. The basic characteristics of the devices presently in operation are reported. The method of averaging over the rapidly varying spatial variable is described. This method is used to study the plasma equilibrium and also the stability with respect to current-driven kink modes and ballooning modes. The limiting plasma pressure, determined jointly by the conditions for plasma equilibrium and stability, is discussed. Methods for raising this limit are described. The present state of the theory of the MHD equilibrium and stability of plasmas in stellarators is summarized. The basic problems for further development of this theory are outlined.

A review of the applications of the scanning electron microscope cathodoluminescent mode is given. Particular attention is devoted to the kind of information that can be obtained by modifying the method in different ways, the problems of spatial resolution and the formation of image contrasts. Results obtained for GaAs, GaP and other optoelectronic materials show the advantages of the local cathodoluminescence method in determining local values of electrophysical parameters in multilayer epitaxial structures, distribution of optically active impurities, etc. These features make the method uniquely useful for the growth of optoelectronic structures with prescribed properties.