Faculty of Physics
M.V.Lomonosov Moscow State University
Solid state physics

## Pulsed magnetization reversal in ferrite-garnet films

### O.S. Kolotov, V.A. Pogozhev

Moscow University Physics Bulletin 1991. 46. N 5. P. 5

The literature devoted to the problem of pulsed magnetization reversal in ferrite-garnet films is briefly surveyed. The main attention is given to the flux reversal in films exposed to spatially uniform fields oriented along the easy axis. The mechanisms of pulsed magnetization reversal and their manifestation in the behavior of the principal characteristic of a material - the pulsed flux reversal curve - are considered. The effects of structural imperfections (defects and stratification) present in real ferrite-garnet films on their magnetization behavior are discussed. Problems that require further investigation are formulated.

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Theoretical and mathematical physics

## On resonance properties of the energy operator of a many-particle system in an external field

### V.G. Airapetyan$^1$, V.V. Komarov$^1$, A.M. Popova$^1$, H. Neumann$^2$

Moscow University Physics Bulletin 1991. 46. N 5. P. 19

The scaling method is applied to take into account the effect of an external field on the parameters of two-particle resonance phenomena in the final state of many-particle nuclear reactions.

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## Propagation of perturbations in an elastic-plastic nondissipative medium

### V.L. Popov

Moscow University Physics Bulletin 1991. 46. N 5. P. 23

Propagation of elastic-plastic waves has been considered in terms of the simplest gauge theory of an isotropic elastic-plastic nondissipative continuum. It is shown that, in the course of time, a perturbation produced by a short impact breaks into six groups of waves having different character of propagation.

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## The dynamics of a broad spectrum of oscillations in scattering of electromagnetic waves by a relativistic beam

### Yu.V. Bobylev, V.A. Panin, A.P. Plotnikov

Moscow University Physics Bulletin 1991. 46. N 5. P. 27

The nonlinear theory of scattering of multimode electromagnetic oscillations by a relativistic electron beam is examined. The principal stabilization mechanism for the instability that arises under anomalous Doppler effect is based on the following two effects: the beam retardation and the relativistic dependence of the plasma oscillations frequency of the beam on the amplitude. In the case of monochromatic pumping, the spectrum of the scattered wave is shown to broaden as the relativistic character of the beam grows. With a nonmonochromatic pumping, an effective excitation of the monochromatic signal wave takes place, with a process efficiency reaching 50-60%.

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## On the theory of quasilinear relaxation of an electron beam emitting under conditions of collective Cerenkov effect

### M.V. Kuzelev, V.A. Panin

Moscow University Physics Bulletin 1991. 46. N 5. P. 33

Multi-mode beam instabilities which develop in the conditions of the collective Cerenkov effect have been studied by quasilinear theory methods. The quasilinear approach is shown to be equivalent to the method of characteristics of the Vlasov equation as applied to the description of relaxation of the multi-mode beam instabilities. The excitation of a wide spectrum of electromagnetic oscillations by a dense beam in a retardation system has been studied. Besides, an equation of the Fokker-Planck type has been derived which describes the diffusion of electrons in a space of velocities, and also the laws of conservation of energy and momentum in the particle-field system.

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## Dynamics of relativistic electrons in a nonadiabatic undulator with guide magnetic field

### A.F. Aleksandrov, V.L. Vesnin, V.A. Kubarev, V.A. Cherepenin

Moscow University Physics Bulletin 1991. 46. N 5. P. 39

A nonlinear theory is developed for a detailed investigation of the dynamics of relativistic electrons in nonadiabatic undulators with a guide magnetic field. The nonlinear resonance curves differ qualitatively from those obtained for adiabatic undulators. In the region of resonant magnetic fields, which are of the greatest interest, there are no stationary electron trajectories in both cases. The distinctive features of the electron dynamics are examined for active and passive systems. It is shown that the application of nonadiabatic undulators provides a much stronger twist of the beam as compared to adiabatic undulators and looks promising for microwave devices with transverse interaction, particularly for those using resonance scattering.

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Optics and spectroscopy

## Synthesis of wideband multilayer metal-dielectric coatings

### N.V. Grishina

Moscow University Physics Bulletin 1991. 46. N 5. P. 44

The problem of obtaining wideband multilayer metal-dielectric coatings with desired spectral properties is considered. Using an earlier developed approach, we have synthesized high-performance heat-reflecting cut-off filters with silver and copper interlayers, and a low-reflectance coating with a transmission coefficient about 10% in the visible range, using nickel interlayers.

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Solid state physics

## A method for improving the sensitivity of X-ray reflectometry

### M.N. Orudzhaliev, V.A. Bushuev

Moscow University Physics Bulletin 1991. 46. N 5. P. 49

A new method is proposed for determining the degree of roughness of a solid surface using the phenomenon of multiple X-ray total external reflection from the walls of a band-shaped waveguide. It is shown that the angular dependence of the waveguide transmission coefficient is more sensitive to the root-mean-square height of roughness than the curve of the single reflection coefficient. The dependence of the transmission coefficient on the X-ray guide parameters is analyzed.

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## The Mott transition and electron pairing in a strong electromagnetic field

### V.D. Blazhin

Moscow University Physics Bulletin 1991. 46. N 5. P. 54

The feasibility of inducing a Mott's metal-insulator transition in narrow-band crystals by a strong constant or alternating electric field is shown. The tow-electron approximation has been applied to consider the problem of formation of a small-radius electron pair in a constant electric field in such crystals, and the idea of electromagnetic pumping, analogous to laser pumping, of superconducting condensates is formulated.

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## Electrical resistivity and Hall effect in amorphous $Cu_{1-x}Zr_x$ alloys in the $s-d$-model (the coherent locator approximation)

### A.V. Vedyaev, A.B. Granovskii, I.Kh. Khalilov, S.A. Ninalalov, D.Kh. Imamnazarov, M.M. Gekhtman, Jr

Moscow University Physics Bulletin 1991. 46. N 5. P. 59

The electronic structure, the electrical resistivity, and the Hall coefficient of amorphous $Cu_{1-x}Zr_x$ alloys were calculated in the framework of the coherent locator approximation for the $s-d$-model with consideration for the off-diagonal disorder. The calculation results on the concentration dependence of the electrical resistivity and the Hall coefficient are in agreement with the available experimental data.

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Geophysics

## Fair-weather field and the baroelectric effect

### V.I. Grigor'ev, E.V. Grigor'eva

Moscow University Physics Bulletin 1991. 46. N 5. P. 66

The electric field generated by the action of tidal forces on the Earth via the baroelectric effect, viz., the effect of redistribution of electrons in a nonuniformly stressed, chemically homogeneous isothermal conductor, was theoretically investigated. The field studied is compared with the fair-weather field over the Earth's surface and the conclusion is drawn that the existence of the fair-weather field can be explained in general terms without the assumption: that the Earth carries a considerable negative charge.

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Theoretical and mathematical physics

## Emission of a sneutrino pair by a charged lepton in strong magnetic fields

### E.V. Merzonova, A.I. Studenikin, I.M. Ternov

Moscow University Physics Bulletin 1991. 46. N 5. P. 72

The process of emission of a sneutrino pair by a charged lepton in an external magnetic field has been studied. Expressions for the probability of the $l’ \to l +\tilde{\nu_{l’}}+\tilde{\bar{\nu_l}}$ process in a strong magnetic field have been derived and the effect of one-dimensionalization is shown to take place in this case.

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## On cylindrically symmetric and static solutions in relativistic gravitation theory

### J.E. Pinzon (Colombia)

Moscow University Physics Bulletin 1991. 46. N 5. P. 75

It is shown that the cylindrically symmetric and static Levi-Civita solution in relativistic gravitation theory (RGT) is nonphysical.

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## Optimal two-impulse transfers to the libration point $L_2$ of the Sun-Earth system with the use of asymptotic trajectories

### A.I. Subaev

Moscow University Physics Bulletin 1991. 46. N 5. P. 105

It is shown that energy expenditures for a transfer from a near-Earth circular artificial satellite orbit to the libration point $L_2$ of the Sun-Earth system can be reduced, if asymptotic trajectories are used.

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Optics and spectroscopy

## Study of photoluminescence of cadmium sulfide doped with indium

### A.N. Obraztsov, F. Terra

Moscow University Physics Bulletin 1991. 46. N 5. P. 77

Photoluminescence of cadmium sulfide obtained by condensation from the vapor phase on a glass substrate has been studied. The results obtained support the model of optical excitation recombination in CdS heavily doped with indium. The model is based on the assumption of existence of doubly charged centers related to cadmium vacancies in the lattice of the $V^{2-}_{Cd}$ type.

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Acoustics and molecular physics

## A method of correcting amplitude and phase errors in the operation of multicomponent acoustic rate meter

### 0.A. Kharin, S.V. Kholodova

Moscow University Physics Bulletin 1991. 46. N 5. P. 80

A method has been suggested of the acoustic rate meter calibration which makes it possible, at the stage of computer processing, to compensate for the amplitude and phase errors due to a mismatch between the microphones. The experimental data are presented that demonstrate the method efficiency.

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Solid state physics

## Twinning of martensite phase crystals

### A.G. Khundzhua, A.V. Sorokin, E.V. Chernov

Moscow University Physics Bulletin 1991. 46. N 5. P. 83

Crystallographic features of twinning have been studied in a system of martensite crystals generated from an initial single crystal as a result of phase transformation. It is shown that twinning in alloys with the effect of shape memory leads to a transition from one type of orientational relationship to another, crystallographically equivalent type.

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## The structure and magnetoelastic properties of rare-earth Laveis phases of the C15 type

### G.V. Bondar'kova, A.S. Ilyushin, I.A. Nikanorova

Moscow University Physics Bulletin 1991. 46. N 5. P. 86

The results of a theoretical calculation of spin-orientation magnetic phase diagrams are presented for some sections of the $(Tb_{1-x}Ho_{x}) _{1-y}Dy_yAl_2$ system, and the temperature and concentration dependences of the energy of magnetocrystal anisotropy are demonstrated.

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## Effect of pressure on magnetic susceptibility of high-purity single crystals of rare-earth metals

### S.A. Nikitin, Yu.I. Spichkin, A.M. Tishin, 0.D. Chistyakov

Moscow University Physics Bulletin 1991. 46. N 5. P. 90

Data obtained from the study of the effect of cubic compression on the magnetic susceptibility in high-purity rare-earth metals are used to determine the temperature shift of magnetic phase transitions upon pressure variation. The variation of indirect exchange integrals was calculated for the rare-earth metals Gd, Tb, Dy, Ho, and Er following a reduction of their atomic valumes.

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## Microstructure of sputter-deposited multilayer Ta/Al films with superlattice

### A.S. Ilyushin, N.A. Khatanova, Wu Zi-Qin (China), Yuan Xiang-yang (China)

Moscow University Physics Bulletin 1991. 46. N 5. P. 94

X-ray diffraction and electron microscopy have revealed that in deposition of multilayer Ta/Al films onto glass substrates, the near-substrate layer has an amorphous structure, while subsequent crystalline layers of Ta and Al exhibit a planar axial texture. The films show the presence of a superlattice with a period of 72 A. After annealing at 550°C, the two-layer microstructure transforms to a four-layer one.

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Geophysics

## Estimating the characteristic lifetime of planetary atmospheres

### E.V. Pavlova, Yu.P. Pyt'ev

Moscow University Physics Bulletin 1991. 46. N 5. P. 98

An equation is written for the general case of nonstationary gas motion in a spherically symmetric gravitational field. The equation solution corresponding to the steady-state radial flow in the medium is analyzed. It is shown that the characteristic lifetime of a planetary atmosphere depends exponentially on a parameter equl to the ratio of the product of the gravitational acceleration by the planet radius to the atmospheric temperature.

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## Estimation of the effect of irregular shifts of the ocean bottom on the mean slope of the ocean surface

### S.V. Makeev, V.I. Pavlov

Moscow University Physics Bulletin 1991. 46. N 5. P. 102

The mean square of the slope of a wavy ocean surface is known to differ from zero even in the absence of wind. It is shown that practically for the entire water area of the World Ocean this phenomenon can be accounted for by the influence on the ocean surface of persistent irregular seismic shifts of the ocean bottom. Numtrical estimates of the expected effect are presented.

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