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1.
The excitation of axial radio-frequency (rf) magnetic induction by an axial rf current is observed in a conductor with circular
magnetic anisotropy when a weak magnetizing field is applied. The conductor is an amorphous cobalt-based wire, which exhibits
azimuthal magnetic anisotropy. It serves as the central conductor in a coaxial line. The axial rf magnetic induction produces
an emf in an induction coil coaxial to the conductor. The induction coil is part of a matched receiving circuit. The power
conversion coefficient is as high as tens of percent. The measurements demonstrate the high sensitivity of the conversion
coefficient to an external field. The theory of ferromagnetic resonance faithfully describes the results of the observations.
Zh. Tekh. Fiz. 69, 58–63 (March 1999) 相似文献
2.
A self-similar solution is obtained for the self-consistent hydrodynamic equations describing the motion of an ellipsoid of
charged particles in a Penning trap and in an rf trap. The conditions are determined for which a small periodic variation
of the confining magnetic field in the Penning trap drives oscillations of the bunch.
Zh. Tekh. Fiz. 67, 27–29 (January 1997) 相似文献
3.
The coherent repopulation of a quantum system consisting of three nonequidistant levels in the field of a resonant bichromatic
rf wave is studied. The atoms are assumed to have an impulsive interaction with the rf wave in which the pulse duration is
less than any of the relaxation times. The hyperfine structure of gas atoms and a system of atomic oscillator levels in a
magnetic trap are considered as examples of such a quantum system. It is shown that in the second case, the coherent repopulation
effect can be used to cool neutral atoms in magnetic traps.
Zh. éksp. Teor. Fiz. 113, 1181–1192 (April 1998) 相似文献
4.
V. A. Lisovskii 《Technical Physics》1998,43(5):526-534
It is found that the region for the stable existence of the aregime of a radio-frequency (rf) discharge is bounded not only
on the moderate-pressure side, but also on the low-pressure side. One feature of the α-γ transition in a low-pressure rf discharge is that the criterion for breakdown of the electrode sheath is not satisfied. It
is shown that at low pressures the α-γ transition of an rf argon discharge takes place abruptly and exhibits hysteresis. At intermediate pressures the α-γ transition is continuous and lacks jumps; negative differential conductivity appears, double layers form, and nonmonotonic
behavior of the plasma density is observed at the center of the discharge. The role of stochastic (collisionless) electron
heating in sustaining an rf discharge at intermediate gas pressures is discussed.
Zh. Tekh. Fiz. 68, 52–60 (May 1998) 相似文献
5.
K. O. Khutsishvili N. P. Fokina G. Eska 《Journal of Experimental and Theoretical Physics》1998,87(5):996-1002
An investigation based on the coupled Maxwell-Bloch equations for a system of equivalent exchange-coupled spins is performed
in order to explain a number of features of NMR spectra obtained in metals by Fourier-transforming of the free-induction decay
at ultralow temperatures. Small angles of tilting of the nuclear magnetization by the exciting rf field are considered. It
is shown that the free precession inherits the nonuniformity in the distribution of the rf field and the magnetization produced
at the excitation stage inside the sample on account of the skin effect. As a result, the NMR spectrum is found to consist
of a set of peaks—signals due to standing spin waves. However, such a spectrum can be observed only when the detuning of the
exciting rf field is sufficiently large relative to the Larmor frequency of the spins. Otherwise, the rf field does not penetrate
into the sample because of strong absorption by the spins. If the detuning is large, the dispersion signal and part of the
NMR absorption signal are proportional to the equilibrium magnetization to the power 3/2. Such behavior is expected at low
temperatures so that the coupling of the magnetization with the rf field is strong. The results obtained qualitatively explain
the experimentally observed characteristics of the NMR spectra: the presence of kinks and structure of the NMR lines, the
dependence of the shape and intensity of the spectrum on the detuning of the exciting rf field, and the nonlinear dependence
of the nuclear susceptibility on the reciprocal of the sample temperature.
Zh. éksp. Teor. Fiz. 114, 1836–1847 (November 1998) 相似文献
6.
A contact-free method of modulation spectroscopy of semiconductor heterostructures is developed. The method employs the effect
of an intensity-modulated rf or microwave field on the reflection of the probe light and makes it possible to investigate
electron-hole interaction effects in different layers of a heterostructure. A model is proposed which explains the characteristic
features of the rf-modulated optical reflection spectra observed on selectively doped GaAs/AlGaAs heterostructures is proposed.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 3, 217–221 (10 February 1998) 相似文献
7.
A simple analytical model is presented making it possible to determine the amplitudes and phases of the rf field in the electrode
sheaths and quasineutral plasma of an rf discharge in the presence of electronneural collisions. The collisional case ω≪ν
is considered in detail. Measurements are also made of the electron temperature, plasma density, thickness of the electrode
sheaths, and rf field amplitude in the quasineutral plasma of an rf discharge in argon. The rf field amplitudes predicted
by this model are in satisfactory agreement with both our experimental data and the results of theoretical calculations of
other authors.
Kharkov State University, Kharkov. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 41, No. 12, pp. 31–38,
December, 1998. 相似文献
8.
9.
Unusual piezoresponse signals have been observed in glycine aminoacid powder at a frequency near 10 MHz, which exhibited a
regular pattern in time determined by a periodic phase variation in the elastic vibrations of individual powder particles.
This phenomenon results from the formation of spatial structures in glycine powder under the action of a strong rf field.
Fiz. Tverd. Tela (St. Petersburg) 40, 1086–1089 (June 1998) 相似文献
10.
The “rf collapse” effect is used to determine the quadrupole splitting distributions in ferromagnetic amorphous FexCo78-xSi9B13 alloys. The rf field induces crystallization of amorphous alloys which, for x<60 at.%, suppress the rf collapse. 相似文献
11.
Two-pulse and three-pulse echoes in powdered yttrium and bismuth high-T
c superconductors are investigated to determine the dependence of the signal amplitude on the magnetic field, the temperature,
and the gas pressure. The temperature is measured as a function of the relaxation time of the echo signal. The properties
of the long-lived rf echo are studied in detail; it exhibits a persistent (lasting more than several hours) memory of a time
series of write pulses and a cumulative storage effect. The experimental results can be explained qualitatively within the
framework of the theory proposed by Asadullin [Sverkhprovodimost’ 6, 545 (1993)] to account for the nonlinear motion of vortices associated with sample defects.
Zh. éksp. Teor. Fiz. 111, 1032–1046 (March 1997) 相似文献
12.
The equivalent parameters of a Josephson junction in a microwave SQUID structure are calculated on the basis of relations
obtained as a result of an analysis of the operation of an rf SQUID. This analysis is based on the sawtooth variation of the
voltage on the resonator as a function of the constant flux bias. The quantitative characteristics permit regarding the Josephson
junction as a linear impedance in the rf or microwave circuit, whose real and imaginary parts are controlled by the constant
magnetic flux passing through the SQUID loop.
Zh. Tekh. Fiz. 69, 106–112 (November 1999) 相似文献
13.
A study is made of the production of high power nanosecond rf pulses by extracting microwave energy from an oversized cavity
by means of conversion, at a coupling window, of the high-Q working mode to an auxiliary mode which is strongly coupled to
an external load. It is shown that microwave rf pulse compressors with copper storage cavities and energy extraction by mode
conversion at a coupling window can provide gains of 5–13 dB with output signal durations of 20–150 ns and peak powers of
5–10 MW in the 3-cm band and 50–100 MW in the 10-cm band. Rf pulses lasting 30 ns with peak powers of 0.5 MW have been obtained
experimentally at a frequency of 9.4 GHz with a gain of 9 dB.
Zh. Tekh. Fiz. 68, 92–96 (July 1998) 相似文献
14.
An rf power compressor is proposed which contains two standing-wave cavities mounted to the side wall of the waveguide to
form amplified rf pulses.
Zh. Tekh. Fiz. 69, 119–120 (January 1999) 相似文献
15.
Starting from an analytical macroscopic/phenomenological model yielding the self-bias voltage as a function of the absorbed
radio-frequency (rf) power of an asymmetric capacitively coupled discharge in NF3 this paper studies the dependence of the ion flux onto the powered electrode on the gas pressure. An essential feature of
the model is the assumption that the ions' drift velocity in the sheath near the powered electrode is proportional to E
α, where E=−ΔU (U being the self-bias potential), and α is a coefficient depending on the gas pressure and cross section of elastic ion-neutral
collisions. The model also considers the role of γ-electrons, stochastic heating as well as the contribution of the active
electron current to the global discharge power balance. Numerically solving the model's basic equations one can extract the
magnitude of the ion flux (at three different gas pressures) in a technological etching device (Alcatel GIR 220) by using
easily measurable quantities, notably the self-bias voltage and absorbed rf power. 相似文献
16.
V. M. Mukhortov Yu. I. Golovko G. N. Tolmachev A. I. Mashchenko 《Technical Physics》1999,44(12):1477-1480
New experimental data on the characteristic features of the synthesis and crystallization of films of solid solutions of lead
zirconate-titanate, deposited by means of rf diode sputtering of ceramic targets, are presented. Such a deposition system
possesses threshold states, transition through which leads to a qualitative change in the processes occurring in the system
and to the appearance of self-organization effects. The basic feature of this change is determined by the appearance of a
new structured system, consisting of the sputtered particles and particles formed in the plasma, in the plasma of an rf discharge.
Zh. Tekh. Fiz. 69, 87–91 (December 1999) 相似文献
17.
D. A. Kostarov N. P. Fokina K. O. Khutsishvili 《Journal of Experimental and Theoretical Physics》1997,85(2):300-306
We propose a model of radiofrequency (rf) superradiance by a system of interacting nonequivalent spins in a point specimen.
In contrast to the rf superradiance observed and described earlier, here spin-spin coupling acts as the interaction with the
cavity. To be definite, we examine the spins of two isotopes of a metal that are coupled by the Ruderman-Kittel interaction.
The analysis of such a system when the magnetization of one spin species is inverted shows that the system can have one resonance
frequency and two different decay times, instead of two resonance frequencies and one decay time in the usual situation. When
such “repulsion” of decay times occurs and the absolute values of the spin polarizations are large, transverse magnetization
increases and exhibits features characteristic of superradiance. Finally, we calculate the parameters of this superradiance:
the voltage across the terminals of an rf pickup coil, the pulse length, the delay time, and the superradiant intensity.
Zh. éksp. Teor. Fiz. 112, 551–563 (August 1997) 相似文献
18.
A contactless microwave method is used to measure the fast magnetic relaxation of granular ceramic samples of YBa2Cu3O7−x
irradiated by neutrons with fluences of 1016–1019 cm−2. An experimental study of the time dependence of the relaxation of high-frequency (rf) absorption (f=100 MHz) after the action of an external magnetic field pulse has shown the magnetic relaxation times τ
0 to be in the time interval of 0.5–150 ms. The rf-absorption mechanism is discussed in terms of an intergranular system with
a thermally activated flux of vortices and their diffusion in the granular medium.
Fiz. Tverd. Tela (St. Petersburg) 39, 977–981 (June 1997) 相似文献
19.
Yu. I. Golovin R. B. Morgunov V. E. Ivanov S. E. Zhulikov A. A. Dmitrievskii 《JETP Letters》1998,68(5):426-431
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.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 5, 400–405 (10 September 1998) 相似文献
20.
V. M. Mukhortov G. N. Tolmachev Yu. I. Golovko A. I. Mashchenko 《Technical Physics》1998,43(9):1097-1101
New experimental data on the growth mechanisms of multicomponent Pb(Zr,Ti)O3, (Ba,Sr)TiO3, and Y-Ba-Cu-O films in an rf discharge plasma are presented. An investigation of the spatial distribution of the radiated
intensity of the sputtered particles in the rf plasma during the deposition of films of these mixed oxides in the epitaxial
state reveals general laws governing their transport from the target to the substrate, which are stipulated by features of
the negative glow of the rf discharge. The roles of external and internal parameters are examined from the standpoint of describing
the mechanisms of the heteroepitaxial growth of mixed oxides.
Zh. Tekh. Fiz. 68, 99–103 (September 1998) 相似文献