V. V. Kolesnikov

Dynamics of polarization reversal in thin PZT films

New experimental data on the dynamics of polarization reversal in thin PZT films prepared by rf sputtering are reported. The frequency and amplitude dependences of the hysteresis loop area and coercive field are investigated. It is shown that, at infralow frequencies, there exists a critical frequency at which the shape of the hysteresis loop changes stepwise. Theoretical analysis of the related problems is given.

Stress-induced domain structure formation in nanodimensional barium strontium titanate films

Thin heteroepitaxial films of BaxSr1−xTiO3 (BST) with x = 0.80 possessing high structural perfection have been grown by RF magnetron sputtering on MgO(001) substrates. The microstructure and crystallographic characteristics of the BST films of various thicknesses have been studied using electron microscopy and X-ray diffraction. It is established that there is a threshold thickness at which the BST crystal lattice parameter in the direction perpendicular to the substrate exhibits a sharp change.

Geometrical effects in nanodimensional epitaxial films of barium strontium titanate

The effect of the thickness of 6- to 950-nm-thick Ba0.8Sr0.2TiO3 films epitaxially grown on (001)MgO on their ferroelectric properties is investigated. Raman scattering and X-ray diffraction data indicate a structural phase transition taking place at a film thickness of ≈70 nm, which changes drastically the lattice parameters of the film. Raman spectra taken of the films confirm that they are in the ferroelectric state and that their symmetry changes in going over a critical thickness, as revealed by a sharp displacement of the peaks corresponding to the A1(TO) and E(TO) components of the soft mode. At film thicknesses of <100 nm, the permittivity versus thickness dependence exhibits two peaks at thicknesses of ∼18 and ∼36 nm. Near the first peak, the dielectric nonlinearity is considerably higher than near the second one.

Parameters of charged-particle tracks in the P-type nuclear emulsion

TheZ2/β2 parameter (Z is the charge and β is the particle velocity in terms of the light velocity) for protons, α-particles, and nuclei was measured in the P-type nuclear emulsion with an optical microscope and the MAC-1 semiautomatic system. TheZ2/β2 measurement range was extended to the value β=0.1. The results obtained with the MAC-1 system and the visual processing methods agree up toZ=ZSi Tracks of up to Au nuclei can be investigated now with the MAC-1 system.

On the possibility of observing low-intensity spectral lines of internal conversion electrons using the MAC-1 setup

Results of upgrading of MAC-1 setup components are described. It is shown that the optimum conditions for detection of low-intensity spectral lines are ensured by the high sensitivity of the instrument to gradations of photoemulsion blackening and by the high resolution of the optoelectronic channel that forms the image of emulsion grains, in combination with the possibility of varying the spectrogram scanning modes, which has been provided by the upgrading. The upgrading of the instrument opens up new avenues for spectroscopy of internal conversion electrons if sufficient statistics is acquired in an experiment. The efficiency of the proposed procedures is demonstrated by the example of extraction of low-intensity K672.35 160Dy and K673.09 160Dy lines in a spectrogram of internal conversion electrons from erbium fractions.

Processing of tracks and beta-ray spectrograms with the MAS-1 universal setup

Results of processing photoemulsion plates exposed in several experiments that were performed on the MAS-1 automated complex with a microscope are reported. Specifically, the case of detecting a charmed meson in the WA-95 (CERN) experiment is considered. Also, the processing of internal conversion electron spectrograms that are recorded with a beta-ray spectrograph equipped with a precision image-sensing TV system providing an accuracy of 1 µm in three coordinates is described.

Calibration of a Shower Detector with Nuclear Emulsion in an Electron Beam

The production of electron–photon showers in the shower detector was investigated. The detector is composed of alternating layers of nuclear emulsion and lead with a total thickness of 2.95 radiation units for exposure to a 10-GeV electron beam. By using experimental results, it is possible to identify electrons in the shower detector with a high efficiency.

A Technique for Measuring Beta-Spectrograms on a МАС-1 Universal Setup

Methods for processing the photographic spectrograms of internal-conversion electrons are considered. The spectograms were obtained on a beta-spectrograph for rare-earth elements isotopes with the use of a precision TV image-reading system designed in 2000 for the MAC-1 setup.

Cascade multiplication of a 26-GeV electron shower in a lead plate-emulsion sandwich chamber

The electron-photon shower development in a lead plate-emulsion sandwich chamber with a total effective lead thickness of 3.5 radiation units was studied for an electron energy of 26 GeV. The experimental electron multiplication coefficient (Pexp=19.4±1.4) agrees with a theoretical value (Pcalcd=20.4) calculated with corrections for the particle scattering and absorption.