Ion diffusion-controlled thermally stimulated processes in X-ray irradiated halide crystals

The ionic and ion diffusion-controlled thermally stimulated relaxation (TSR) processes in CaF 2 , BaF 2 , LiBaF 3 and KBr crystals were investigated above 290 v K by means of the ionic conductivity, ionic thermally stimulated depolarisation current (TSDC) and thermal bleaching techniques. Under a DC field the halide crystals store large ionic space charge. We were able to detect in CaF 2 , BaF 2 , LiBaF 3 and KBr in the extrinsic ionic conductivity region a series of the ionic defect (the interstitial anion and/or anion vacancies - in fluorides; the cation vacancies - in KBr) release stages: 3-6 wide and overlapping ionic TSDC peaks. The correlated data of the ionic TSDC and the F band thermal evidence that above 290 v K the TSR processes are initiated and controlled by the ionic defect thermal detrapping, migration and interaction with the localised electronic and ionic charges and colour centres. The ion diffusion-controlled TSR processes take place in the above halide crystals.     

Ion diffusion-controlled thermally stimulated processes in x-ray irradiated halide crystals

The ionic and ion diffusion-controlled thermally stimulated relaxation (TSR) processes in CaF₂, BaF₂, LiBaF₃ and KBr crystals were investigated above 290 K by means of the ionic conductivity, ionic thermally stimulated depolarisation current (TSDC) and thermal bleaching techniques. Under a DC field the halide crystals store large ionic space charge. We were able to detect in CaF₂, BaF₂, LiBaF₃ and KBr in the extrinsic ionic conductivity region a series of the ionic defect (the interstitial anion and/or anion vacancies - in fluorides; the cation vacancies - in KBr) release stages: 3-6 wide and overlapping ionic TSDC peaks. The correlated data of the ionic TSDC and the F band thermal show that above 290 K the TSR processes are initiated and controlled by the ionic defect thermal detrapping, migration and interaction with the localised electronic and ionic charges and colour centres. The ion diffusion-controlled TSR processes take place in the above halide crystals.     

Kinetics of thermally stimulated recombination processes in lithium borate crystals

This paper reports on the results of the experimental and theoretical investigations of thermally stimulated recombination processes in crystals of the lithium borates Li₂B₄O₇ and LiB₃O₅. For both types of crystals, the measurements of thermally stimulated luminescence curves, spectra, and temperature dependences of the intensities of steady-state X-ray luminescence have been performed in a single experimental cycle. In the framework of a unified model for the Li₂B₄O₇ and LiB₃O₅ crystals, the thermally stimulated recombination processes have been calculated and the obtained results have been interpreted talking into account all available experimental data.     

On the relation between thermally stimulated depolarization and thermoelectricity in irradiated aluminophosphate glasses

Several reasons are given to assume both the maximum of thermally stimulated depolarization near 100 °C and the thermovoltaic effect in aluminophosphate glasses to be associated with the movement of protons. The assumption, that the glasses are hydrolyzed, is supported by this finding.     

Effects of doping and preliminary processing on the magnetically stimulated mobility of dislocations in InSb single crystals

The effect of the type of conductivity and the doping level of InSb single crystals on the mobility of fast 60° dislocations in a magnetic field is discovered. It is found that doping of a pure InSb crystal with tellurium (n-type impurity) to 10¹⁸ cm^?3 reduces the mobility of dislocations to the background level. At the same time, in p-type InSb crystals doped with Ge with the same carrier concentration (10¹⁸ cm^?3), the magnetoplastic effect is manifested clearly. It is shown that preliminary mechanical loading and, hence, internal stresses in the crystal affect not only the mean path length of dislocations in a magnetic field but also the magnitude of the threshold magnetic field below which the magnetoplastic effect is not observed. Possible reasons for these phenomena are discussed.     

Wave dispersion relation of two-dimensional plasma crystals in a magnetic field

The wave dispersion relation in a two-dimensional strongly coupled plasma crystal is studied by theoretical analysis and molecular dynamics simulation taking into account a constant magnetic field parallel to the crystal normal. The expression for the wave dispersion relation clearly shows that high-frequency and low-frequency branches exist as a result of the coupling of longitudinal and transverse modes due to the Lorenz force acting on the dust particles. The high-frequency and the low-frequency branches are found to belong to right-hand and left-hand polarized waves, respectively.     

Influence of light and magnetic field on dislocation mobility in ionic crystals

We discuss the role of exchange forces between paramagnetic centers in the bulk and on dislocationsd as a determinant of the plastic properties of diamagnetic crystals. It is shown that the movement of individual dislocations may be used as a measure of the intensity of mechanically active radical chemical reactions with a sensitivity to changes in the spin state at the level of one hundred atoms. G. R. Derzhavin University, Tambov. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 31–36, July, 1998.     

Thermo-emf of InSb in a transverse quantizing magnetic field

We have measured the thermo-emf of n-type indium antimonide in a transverse quantizing magnetic field. The results are explained using a theory that includes splitting of the Landau levels.Physics Institute of the Dagestanskii Center, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 26–29, March, 1993.     

Reactivity and dislocation structure of silver-and lead-azide crystals exposed to a variable magnetic field

The physical-chemical processes caused by a variable magnetic field of strength 0.1 T and frequency 10 kHz in nonmagnetic silver-and lead-azide crystals are studied. The experiment shows slow decomposition accompanied with plastic deformation both under the action of the variable magnetic field and in post processes. The dependence of relative volume of gas released during post processes on the magnetic-field frequency is examined. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 103–106, January, 2006.     

Effect of a magnetic field on thermally activated tunneling ionization of impurity centers in semiconductors

An expression for the probability of thermally activated tunneling ionization in an electric field in the presence of a magnetic field is obtained. It is shown that the logarithm of the ionization probability is proportional to the squared electric field, and the coefficient of proportionality decreases with increasing magnetic field. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 10, 763–767 (25 November 1998)     

Roles of the magnetic field and electric current in thermally activated domain wall motion in a submicrometer magnetic strip with perpendicular magnetic anisotropy

We have experimentally studied micrometer-scale domain wall (DW) motion driven by a magnetic field and an electric current in a Co/Pt multilayer strip with perpendicular magnetic anisotropy. The thermal activation energy for DW motion, along with its scaling with the driving field and current, has been extracted directly from the temperature dependence of the DW velocity. The injection of DC current resulted in an enhancement of the DW velocity independent of the current polarity, but produced no measurable change in the activation energy barrier. Through this analysis, the observed current-induced DW velocity enhancement can be entirely and unambiguously attributed to Joule heating.     

The field fluctuational model of thermally stimulated processes in ferroelectric LiNbO3

The thermally stimulated processes in the x-irradiated LiNbO₃ crystals were studied by the fractional glow technique. The trap ionization with unusually high values of the mean activation energy and the effective frequency factor as well as decreasing the activation energy of the traps when the temperature increased from 150–180 K were observed. We suggest that all these effects are due to the ion-fluctuation process (the electric field generated by thermal reorientation of dipoles.     

Effect of a magnetic field on thermally stimulated ionization of impurity centers in semiconductors by submillimeter radiation

The probability of electron tunneling from a bound state into a free state in crossed ac electric and dc magnetic fields is calculated in the quasiclassical approximation. It is shown that a magnetic field decreases the electron tunneling probability. This decreases the probability of thermally activated ionization of deep impurity centers by submillimeter radiation. The logarithm of the ionization probability is a linear function of the squared amplitude of the electric field and increases rapidly with the frequency of the electric field.     

On the interaction of stimulated spin-flip raman scattering and stimulated recombination radiation in InSb

We have studied the interaction of stimulated spin-flip Raman scattering and stimulated recombination radiation in n-InSb using a CW CO pump laser. A change in linewidth and output power of second Stokes spin-flip radiation is observed when the tuning curve of the first Stokes stimulated spin-flip radiation and the stimulated recombination radiation cross. The observations are explained using a simple rate equation model.     

The pre-exponential factor of the escape probability in thermally stimulated processes

The pre-exponential factor of the transition probability of a trapped charge carrier into an excited state is evaluated from two different approaches. The semi-classical treatment based on a thermodynamical concept involves the calculation of the vibrational entropy change from the partition sum. The quantum-mechanical treatment deals with non-radiative transitions due to electron-phonon coupling. The factor is found to be explicitely dependent on both the temperature and the lattice vibration frequencies represented by a single Einstein oscillator. In addition, the results from different concepts show similar behaviour. As a consequence the effect of lattice vibrations on the position as well as on the shape of glow peaks in thermally stimulated measurements are investigated on a simple phenomenological base. The analysis of some experimental results can be performed in accordance with the theoretical predictions.     

The role of thermally activated processes in the formation of magnetosensitive point-defect complexes in NaCl: Eu single crystals

The formation of magnetosensitive point-defect complexes in NaCl: Eu crystals is investigated. It is shown that the formation of intermediate metastable magnetosensitive point-defect complexes and their subsequent spontaneous transformation into relaxation products are thermally activated processes and do not depend on the diffusion mobility of impurity-vacancy dipoles. It is revealed that the magnetic field induces a transition of the magnetosensitive point-defect complexes to a new state that cannot occur in the absence of a magnetic field. A variation in the heat treatment temperature makes it possible to enhance the magnetoplastic effect significantly (by a factor of three) and to create the appropriate conditions for the existence of magnetosensitive complexes in the crystal over a long period of time.     

Thermoluminescence and thermally stimulated currents in PbMoO4 crystals

Thermally stimulated depolarization (TSD) currents have been studied in the range from 4 K to room temperature by utilizing direct contacts as well as blocking contacts. Charge carrier injection and subsequent trapping seem to be responsible for internal electric fields. A glow peak near 186 K arises from a dipolar relaxation. The results of additional optical excitation during polarization provide some more information on charge transport involved in relaxation processes. The correlation to the results of photoconductivity and annealing procedure leads to the assumption of oxygen vacancies as the dominant defect centres. The study of thermoluminescence (TL) after X-irradiation gives evidence on defect states in question. In addition, from the results quasi-free charge carriers are assumed to be thermally generated above 100 K.     

Resonant dislocation motions in NaCl crystals under EPR conditions in the Earth’s magnetic field with a radio-frequency pump field

Three resonant peaks l(ν) of dislocation paths, appearing in NaCl crystals under simultaneous exposure to the Earth’s magnetic field B Earth and an ac pump field $$\tilde B$$ have been observed in the radio-frequency range (ν ∼ 1 MHz). Each peak corresponds to a specific experimental geometry. Resonance frequencies correspond to ordinary EPR conditions in which, however, instead of the total Earth’s field, its projections onto particular crystallographic directions play part. These directions are probably related to orientations of magnetic moments at impurity centers in dislocation cores. A physical model describing well the positions all three EPR peaks l(ν) is proposed. The peak height l m is proportional to the squared amplitude of the pump field and the time t of sample exposure to crossed fields: $$l_m \propto \tilde B_m^2 t$$ . The threshold amplitude $$\tilde B_m^{th} \sim 1 \mu {\rm T}$$ of the pump field is detected, below which the effect rapidly disappears. The time of spin-lattice relaxation of radical pairs on dislocations is estimated by the threshold field $$\tilde B_m^{th}$$ level.