V. I. Alshits

Magnetoplastic Effect: Basic Properties and Physical Mechanisms

This paper presents a review of the main results of investigations into the magnetoplastic effect, which manifests itself in motion of dislocations in crystals exposed to magnetic fields. The dependences of the mean free path of dislocations on the induction and direction of the magnetic field, the magnetic treatment time, the temperature, and the type and concentration of impurities are studied for NaCl, LiF, CsI, Zn, Al, and InSb crystals. The threshold magnetic field Bc below which the effect is absent, the saturation field B0 above which the mean free paths of dislocations remain constant with an increase in the magnetic induction B, and the critical frequency vc of rotation of a sample in the magnetic field above which the effect disappears are examined. The quantities Bc, B0, and vc are investigated as functions of the basic physical parameters. It is found that the magnetoplastic effect is highly sensitive to X-ray radiation at low doses and to simultaneous action of an electric field or mechanical loading. The hardening of NaCl(Pb) crystals in the magnetic field is revealed. The theoretical interpretation is proposed for all the findings and dependences observed.

New data on the physical properties of Y3Al5O12-based nanocrystalline laser ceramics

Microhardness and fracture toughness of highly transparent Y3Al5O12-and Y3Al5O12: Nd3+-based nanocrystalline ceramics are measured for the first time. For the Y3Al5O12: Nd3+ laser ceramics, the use of a longitudinal scheme with a diode-laser pumping at a wavelength of 1.3186 mm (4F3/2 → 4I13/2 channel) enabled one to attain an output power of continuous-wave lasing of ∼3.7 W with 35% efficiency.

Elastic waves in anisotropic plates: short-wavelength asymptotics of the dispersion branches vn(k)

Abstract The dispersion spectra of elastic eigenwaves in infinite plates of unrestricted anisotropy are analytically studied in the short-wavelength approximation. The three boundary problems are solved, for the free (i), clamped (ii) and clamped/free (iii) surfaces. It is shown that generally the dispersion curves v n ( k ) with increasing wavenumber k are bunched in the vicinity of only two asymptotic levels of tracing velocity v. The first level relates to the Rayleigh velocity v R and the second level to the limiting velocity v—the lowest tracing velocity for a bulk wave with the energy flux parallel to the surfaces. It is proved that in case (i) there are always two (and only two) dispersion branches v f ± ( k ), which at growing k are exponentially fast approaching the asymptote v = v R , one from above, the other from below. In case (iii) at large k one (and only one) wave branch v c/f 0 ( k ) always exists close to v R , even closer than v f ± ( k ). And for case (ii) the level v = v R is absent in the spectrum v c n ( k ). The other branches for all three boundary problems are described by the common asymptotic dependence v n (k)= v +(An/k) 2 , where A is a known constant. For case (iii) in the particular case of limiting wave with vanishing traction one should replace above An by πA ( n +1/2). Additional asymptotic levels arising due to symmetry or a special choice of the wave propagation geometry are also discussed. It is shown that they disappear after any “triclinic” perturbation of orientations.

AN EXISTENCE CRITERION FOR THE BRANCH OF TWO-COMPONENT SURFACE WAVES IN ANISOTROPIC ELASTIC MEDIA

Abstract A criterion of existence for the branch of two-component Rayleigh waves in an anisotropic medium is deduced. Provided a two-component Rayleigh wave comes into being for some given geometry of the propagation, one needs to check whether a certain algebraic quantity is different from zero. Its non-vanishing ensures that two-component Rayleigh solutions exist in the vicinity of the given geometry on a line in the three-dimensional space of angles specifying the orientation of the surface and the direction of propagation in it.

The influence of magnetic effects on the mechanical properties and real structure of nonmagnetic crystals

This review for the first time systematizes the results of our investigations into the influence of magnetic effects on the mechanical properties and the real structure of nonmagnetic crystals. It is found that the preliminary magnetic treatment of alkali halide crystals leads to a decrease in their solubility and a change in the microhardness and yield stress. The magnetic field strongly affects the macroplasticity of LiF, NaCl, and PbS crystals under deformation in a magnetic field. This is accompanied by a change in the shape of stress-strain curves, a shortening of deformation stages, a change in the hardening coefficients, and a decrease in the yield stress. It is revealed that the magnetic effects exhibit threshold behavior. The yield stress is measured as a function of the magnetic induction and the strain rate. It is established that the magnetic and electric fields have a joint effect on the kinetics of plastic deformation. A kinematic model of the macroscopic magnetoplastic effect is proposed.

2D Electro-Elastic Fields in a Piezoelectric Layer-Substrate Structure

In the previous two chapters we have studied elasticity of piezoelectric plates considering their interactions with surrounding media through boundary conditions. In this chapter a more realistic situation will be studied, namely, we shall extend our theory for a description of 2D fields in piezoelectric films on substrates, which present in a large variety of modern electronic devices being their important element. Before our works [29, 30] such solutions were known only for purely elastic (non-piezoelectric) anisotropic media of the considered type in two cases: for a homogeneous film on a homogeneous substrate [52] and for an inhomogeneous (stratified or graded) coating on a homogeneous substrate [54]. Below we shall derive the corresponding Green’s functions for arbitrary piezoelectric strips on substrates with line sources in the bulk or at the surface. The chapter is based on the publications [29, 30].

Dispersionless surface polaritons in the vicinity of different sections of optically uniaxial crystals

The sectors of propagation directions of dispersionless polaritons localized at the optically uniaxial crystal-optically isotropic medium interface are determined. The region of possible orientations of the crystal surface containing these sectors is revealed. The boundaries of the sector of possible propagation directions are analytically described as functions of the crystal surface orientation with respect to the optical axis of the crystal. Consideration is given to the optimum ratios of permittivities at which the width of the propagation sectors appears to be maximum. It is found that the boundaries of the sectors of polariton propagation along different surfaces change drastically in the limit of small dielectric anisotropy of the crystal.

Change in the microhardness of nonmagnetic crystals after their exposure to the Earth’s magnetic field and AC pump field in the EPR scheme

Changes in the microhardness of ZnO, triglycine sulfate (TGS), and potassium acid phthalate (KAP) crystals after their exposure to crossed ultralow magnetic fields, i.e., the Earth’s field BEarth ≈ 50 μT and the alternating-current field

Anisotropic resonant magnetoplasticity of NaCl crystals in the Earth’s magnetic field

\tilde B \approx 3 \mu {\rm T}