A. A. Dmitrievskii

Electron paramagnetic resonance in a subsystem of structural defects as a factor in the plasticization of NaCl crystals

A change in the macroplastic deformation rate and an increase in the travel distances of edge dislocations are observed in NaCl single crystals placed in crossed dc and rf magnetic fields. The magnetic-field frequencies at which softening maxima are observed correspond to the resonance frequencies of transitions between Zeeman sublevels in paramagnetic complexes of structural defects.

Softening of ionic crystals as a result of a change in the spin states of structural defects under paramagnetic resonance conditions

The purpose of this work was to investigate the plastic properties of Ca-or Eu-doped NaCl and KCl single crystals in crossed constant and microwave magnetic waves under paramagnetic resonance conditions. It was found that when the photon energy of the microwave field equals the Zeeman splitting of the electronic spin sublevels, resonance softening of the crystals, manifested as an increase in the free path of individual dislocations and the macroplastic flow velocity as well as a decrease of the microhardness of the crystals, is observed. It was established that metastable Ca-and Eu-impurity complexes, which are also sensitive to the constant magnetic field in the absence of the microwave field, as well as complexes formed by dislocations and point defects are responsible for resonance softening.

Influence of a weak magnetic field on spin-dependent relaxation of structural defects in diamagnetic crystals

The purpose of the work is to investigate relaxation of residual stresses and metastable point defects and plastic properties of ionic crystals in crossed static and microwave magnetic fields at the paramagnetic resonance condition. It is revealed that coincidence of quantum energy of a microwave field with energy of Zeeman splitting of electronic spin sublevels of paramagnetic centers leads to an increase in relaxation rate of residual stresses and of metastable point defects, and, as a result, to resonant weakening of crystals which manifests itself in an increase of dislocation mobility and macroplastic flow rate, as well as in a decrease of crystal microhardness. It is shown that the metastable Ca and Eu aggregates sensitive to a static magnetic field in the absence of microwave fields are responsible for resonant weakening. The resonance arises in short-lived non-thermalized states of these aggregates excited by thermal fluctuations.

Effect of electric fields on the dynamics of silicon microhardness changes induced by low-intensity β irradiation

Decelerating effect of electric fields on silicon microhardness changes induced by low-intensity (I = 10.4 × 104 cm−2 s−1) β irradiation has been revealed. The threshold character of the electric field effect is found (the effect is absent at electric fields E < 350 V cm−1).

Multistage radiation-stimulated changes in the microhardness of silicon single crystals exposed to low-intensity β irradiation

Radiation-stimulated and postradiation changes in the microhardness of silicon single crystals exposed to irradiation with a low-intensity flux of β particles (I = 9 × 105 cm−2 s−1, W = 0.20 + 0.93 MeV) are studied. It is established that the inversion of the radiation-induced plastic effect occurs at a characteristic irradiation time τc = 75 min; i.e., irradiation of silicon single crystals for a time τ < τc leads to nonmonotonic reversible hardening, whereas nonmonotonic reversible softening is observed under irradiation for a time τ > τc. It is demonstrated that there exists a correlation between the nonmonotonic dependences of the microhardness and the concentration of electrically active defects at acceptor levels with energies Ec − 0.11 eV, Ec − 0.13 eV, and Ec − 0.18 eV on the irradiation time.

The influence of low-intensity beta radiation on crack susceptibility under indentation of silicon

The dependence of the lengths of radial cracks formed during indentation of silicon single crystals on the depth of imprint has been studied using electron microscopy. The influence of low-intensity (I = 105 cm−2 s–1) beta radiation on the crack susceptibility during indenter penetration to a depth of ∼2.5 μm has been revealed.

Changes in the silicon microhardness induced by a low-intensity electron beam

It is shown that nonequilibrium point defects are of primary importance in the changes in the silicon microhardness induced by a low-intensity (I ∼ 105 cm−2 s−1) electron beam. It is found that the necessary condition for softening under low-intensity electron irradiation is the presence of an oxide layer on the surface. The thickness of the surface layer in which anomalous changes in the microhardness are observed is determined by the layer-by-layer etching technique.

Reversible Changes in the Microhardness of Silicon Crystals under Electron Irradiation with Low Doses

Reversible softening of silicon single crystals under β irradiation with low doses (D<1 cGy) is revealed. The peaks observed in the dependence of the microhardness of silicon on the fluence are explained by the multistage competing processes of transformations of radiation-induced defects.

Anisotropy of the optical suppression of the magnetoplastic effect in NaCl single crystals

Anisotropy of the plane-polarized light effect on magnetosensitive point defects in NaCl crystals has been observed. The data obtained may yield the information on the symmetry of the electronic states of these defects.

Radio-frequency paramagnetic resonance spectra, detected from dislocation displacement in NaCl single crystals

Results are reported here of a study of the resonance effect of a constant magnetic field and a variable magnetic field crossed with it on the rate of macroplastic deformation and motion of edge dislocations in NaCl crystals. The frequencies of the variable magnetic field at which the maximum variations in the plasticity of the crystals are observed correspond to the resonant frequencies for transitions between the Zeeman sublevels in paramagnetic complexes of point defects and complexes consisting of a point defect and a dislocation. Analysis of the radio-frequency spectra obtained enabled us to establish the role of intercrystal reactions in the formation of the mechanical properties of the crystals.