Vladimir V Gudkov

Vladimir V Gudkov
Ural Federal University | UrFU · Institute of Physics and Technology

Doctor of Sciences, Professor

About

98
Publications
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409
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Publications

Publications (98)
Article
A new approach is introduced to obtain information about the adiabatic potential energy surface of the Jahn-Teller complexes subject to the T ⊗ (e + t2) problem in doped crystals. It employs simulation of the contribution of the Jahn-Teller sub-system to ultrasonic attenuation with account of three mechanisms of relaxation and subsequent comparison...
Article
The temperature dependences of attenuation and the velocity of ultrasonic waves at frequencies of 26–158 MHz in a CaF2 fluorite crystal at the substitution of Jahn–Teller Cr2+ centers for calcium ions have been studied. An abnormally high relaxation rate, which is two orders of magnitude higher than the relaxation rate in other previously studied C...
Article
Temperature dependence of attenuation of ultrasonic transverse normal modes, polarized propagating along the [110] crystallographic axis in SrF2 crystal doped with Cr²⁺ ions was measured at the frequency of 52–162 MHz in the temperature range of 4–180 K. The results indicated the T2g⊗(eg + t2g) Jahn-Teller effect problem with important impact of qu...
Article
In CaF2 crystal doped with Ni²⁺ ions, attenuation of all the normal ultrasonic modes with the wave vector k||〈110〉 were investigated at 14–161 MHz in the temperature region of 5–120 K. The observed peaks of relaxation origin were interpreted as manifestation of the Jahn-Teller effect subject to the T1g⊗(eg+t2g) problem. The experimental data made i...
Article
Full-text available
A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFe12O19. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe3+ in the high-spin configuration (S = 5/2) and have a non-degenerate ground state. We show that the electron-donor Ti substitution conv...
Article
A method is developed to determine the symmetry properties of strains and the type of Jahn–Teller effect in crystals with impurity ions in a triply degenerate electronic T state. This method is based on a calculation of the isothermal contribution of the impurity subsystem to the elastic moduli of a crystal and the absorption and velocity of normal...
Article
The earlier developed methodology of ultrasonic investigation for determining the parameters of the Jahn–Teller effect (JTE) in impurity centers in crystals is further developed in application to Ni²⁺ impurities in ZnSe : Ni²⁺. For all normal modes propagating along the [110] axis, the temperature dependences of the attenuation of ultrasound are me...
Article
Full-text available
Based on the data analysis of ultrasonic experiments, a novel approach has been developed to explore Jahn-Teller effect (JTE) problems in non-cubic crystals with JT centers without involving additional experimental data beyond the information about the electronic term and crystal symmetry. Distinguished from cubic crystals, the axis of symmetry of...
Article
Magnetoacoustic investigations of the ZnSe:Cr2+ crystal with sphalerite structure, performed in Faraday geometry, show that there is a new channel of relaxation by the Cr2+ Jahn–Teller (JT) centers, induced by the magnetic field. A new method is worked out that allows to extract the relaxation time, either from the temperature changes of the elasti...
Article
The experimental evidence of the defects influence on the optical and elastic properties of single crystal Bi1.5Sb0.5Te1.8Se1.2 has been reported. The extra vibrational excitation is observed in the Raman spectrum near 125 cm−1. Its line width has increased substantially with the increasing temperature, and its frequency shows a sharp softening in...
Article
A new approach to evaluate the relaxation contribution to the total elastic moduli for crystals with Jahn-Teller (JT) impurities is worked out and applied to the analysis of the experimentally measured ultrasound velocity and attenuation in SrF2:Cr2+. Distinguished from previous work, the background adiabatic contribution to the moduli, important f...
Article
We report the effect of magnetic field induced quantum tunneling and relaxation transitions between orthogonal configurations in polyatomic systems where no tunneling is expected. Typical situations of this kind occur in molecular systems and local centers in crystals in ground and excited electronic T states, subject to the T⊗e problem of the Jahn...
Article
Full-text available
Attenuation and phase velocity of ultrasound have been measured in strontium fluoride single crystal doped with chromium in the temperature range of 4 – 185 K at 56 -162 MHz. Anomalies have been found for all the normal modes corresponding to the non-vanishing elastic moduli of a cubic crystal. Interpretation of the observed anomalies has been done...
Article
Full-text available
Temperature dependence of elastic moduli , , and the latter for the piezo-active and non-piezo-active versions, have been measured in the interval of 4 - 180 K at 28 - 262 MHz in a CdSe: Cr2+ crystal. Anomalies below 40 K have been found for all the moduli, except . The interpretation of the results has been carried out involving the Jahn-Teller ef...
Article
Full-text available
Influence on elastic moduli of donor electron d-states of cobalt impurities has been investigated in mercury selenide crystals. Experiments have been carried out at the frequency of 53 MHz in the temperature interval of 1.3–100 K. Softening of the (Formula presented.) modulus below 10 K has been observed in the impurity crystals in contrast with th...
Article
Full-text available
The influence of magnetic fields on ultrasonic attenuation caused by relaxation in Jahn–Teller centers is studied using chromium ions as Zn substitute impurities in the ZnSe crystal as an example. The changes of the position and shape of the relaxation peak with the applied magnetic field induction B were observed in the temperature dependence of t...
Article
A methodology is worked out to retrieve the numerical values of all the main parameters of the six-dimensional adiabatic potential energy surface (APES) of a polyatomic system with a quadratic T-term Jahn-Teller effect (JTE) from the ultrasound experiments. The method is based on a verified assumption that ultrasound attenuation and speed encounter...
Article
Full-text available
The magnetic field dependence of ultrasonic attenuation α(B) of slow shear waves in the ZnSe:Cr2+ crystal at a number of fixed temperatures from T=1.4 K to 20 K in magnetic fields of up to B=14 T was investigated. For magnetic fields B above 5 T we found that the attenuation increases with B monotonically, and at a given temperature it is proportio...
Article
Full-text available
The effects of the interaction of ultrasound with donor d electrons of cobalt impurity atoms at low concentrations in mercury selenide crystals have been investigated. The temperature dependences of the electronic contribution to the absorption coefficient at a frequency of 53 MHz in crystals with cobalt concentrations from 1018 to 1020 cm−3 and in...
Article
Transition-metal-doped semiconductor GaAs crystals are used as model systems for spintronic research, as well as in other applications. To explore the structure and properties of such impurities, we extended the methodology of ultrasonic investigation of the Jahn-Teller effect in dielectric impurity-centers to the study of significantly different s...
Article
We show that the structure, properties, and concentration of vacancies in crystals can be studied by ultrasonic experiments previously employed for impurity centres only. Measurements of the temperature dependence of attenuation and phase velocities of ultrasonic shear waves of 52 MHz propagating along the crystallographic axis [110] of nominally p...
Article
The interaction of ultrasound with CuGa4As in a GaAs:Cu crystal has been experimentally studied. The temperature dependences of the attenuation of all normal ultrasonic modes propagating in the 〈110〉 direction both in doped copper and in nominally pure gallium arsenide crystals have been measured. In the GaAs:Cu crystal, the attenuation peak has be...
Article
Ultrasonic investigation of ZnSe:Cr2+ crystal was carried out at low temperatures in magnetic field applied along the wave vector. The observed anomalies in magnetic field dependences of attenuation and wave number evidence for existence of resonant transitions between the energy levels of the Jahn-Teller tetrahedral complex CrSe4.
Article
The contribution of the Jahn-Teller effect to absorption of an ultrasonic wave by a GaAs crystal doped with copper has been investigated theoretically. The distinguishing feature of the problem under consideration is the existence of two holes in the state of the complex valence band. The magnitude of the tunneling splitting in Jahn-Teller centers...
Chapter
A review is presented of the worked out earlier method that uses ultrasonic experiments to evaluate Jahn-Teller effect (JTE) parameters, mostly linear vibronic coupling constants, in application to impurity centers of dopant crystals. The method employs temperature dependent ultrasound attenuation and phase velocity measurements. Distinguished from...
Article
The temperature dependence of the speed of sound in crystalline mercury selenide with low concentrations of iron impurities is studied. Experiments are conducted in the ranges of concentration and temperature where hybridized electronic states in iron impurities have been observed previously. It is found that at temperatures below 10 K the speed of...
Article
A method is constructed that uses ultrasonic experiments to evaluate the parameters of the Jahn-Teller (JT) effect in impurity centers in crystals. The method is based on measurements of temperature dependent attenuation and phase velocity and does not require assumptions about mechanisms of relaxation. The results are illustrated by measurements p...
Article
Ultrasonic experiment was done at the frequency of 54 MHz on ZnSe:Cr2+ crystal with concentration of the dopand 3.8 × 1018 cm−3. Giant peak of attenuation of slow shear wave propagating along 〈110〉 crystallographic direction was observed at low temperatures (about 13 K). The peak proved to be due to relaxation process in the Jahn–Teller system. Mag...
Article
The temperature dependence of ultrasonic attenuation is proposed to use for determining concentration of dopand in a diluted magnetic semiconductor. This non-destructive method can be used for the crystal in which attenuation is caused by relaxation in the Jahn-Teller system. Attenuation coefficient per the impurity ion β obtained at a fixed freque...
Article
Contribution of the Jahn–Teller system to the elastic moduli and ultrasonic wave attenuation of the diluted crystals is discussed in the frames of phenomenological approach and on the basis of quantum-mechanical theory. Both, resonant and relaxation processes are considered. The procedure of distinguishing the nature of the anomalies (either resona...
Article
The temperature dependence of the absorption and velocity of transverse ultrasonic waves propagating in the [110] direction in a ZnSe:Fe2+ crystal with the iron impurity of n=2.2×1019 cm-3 is investigated in the temperature interval 1.4-100 K at a frequency of 53 MHz. For the slow transverse mode an absorption peak at 7.3 K and a decrease of the ph...
Article
It was experimentally shown that, in a 3d-impurity-doped ZnSe crystal with the zinc blende structure, nanosized ionic shear displacements of the trigonal (ZnSe : Ni, ZnSe : V) and tetragonal (ZnSe : Cr) types arise at temperatures of 300 and 120 K. As the temperature decreases in the range 100.0–4.2 K, the shear elastic moduli C 44 (ZnSe : Ni) and...
Article
Low-temperature anomalies in absorption of the fast transverse and longitudinal ultrasonic waves are revealed in a ZnSe crystal lightly doped (5.6 × 1018 cm−3) with V2+ ions. These anomalies are interpreted as a manifestation of the Jahn-Teller effect. The temperature dependence of the relaxation time of the impurity 3d electrons is established.
Article
The temperature dependences of the elastic moduli C 44 (C 11 − C 12)/2 and C l = (C 11 + C 12 + 2C 44)/2 of ZnSe : V2+ (impurity concentration, 6 × 1018 cm−3) and ZnSe : Mn2+ (9.4 × 1020 cm−3) are measured in the temperature range 1.4–100.0 K at frequencies of 52 and 156 MHz. The temperature dependences of the adiabatic elastic moduli are derived....
Article
The temperature dependences of the elastic moluli and the absorption of ultrasound were investigated in ZnSe:Mn2+, ZnSe:V2+ and ZnTe:Ni2+ crystals. Peak of absorption and softening of the elastic modulus C44 were found at low temperatures in crystals with the 3d impurities that had orbitally degenerate states. The observed anomalies were interprete...
Article
Temperature dependences of elastic moduli and ultrasonic attenuation were investigated in ZnSe:V2+ and ZnSe:Mn2+ crystals as functions of temperature in the interval of 1.4–100 K for frequencies of 52–270 MHz. A peak in the attenuation was found in ZnSe:V2+ below 4 K for fast shear and longitudinal waves propagating along the [110] crystallographic...
Article
Full-text available
The temperature dependences of the absorption coefficient and phase velocity of 52-MHz ultrasonic waves in iron-doped mercury selenide crystals are studied. The presence of impurities in concentrations of about 1019 cm−3 is found to initiate the appearance of a resonance peak in the absorption coefficient at a temperature of about 5 K and the corre...
Article
Full-text available
We have studied the propagation of transverse ultrasonic waves with a frequency of 52 MHz in an iron-doped mercury selenide (HgSe:Fe) crystal with an impurity concentration of 1019 cm−3, for which the effects of resonant electron scattering on the impurity are most pronounced in the conduction behavior. The temperature dependences of the absorption...
Article
The structure of semiconductor crystals Zn1−x V x2+Se (x = 0.0018) and Zn1−x Cr x2+Se (x = 0.0006) was studied for the first time using thermal neutron diffraction at 300 and 120 K. The diffraction patterns of the crystals were revealed to contain diffuse scattering regions near the Bragg reflections of the initial cubic lattice. The experimental r...
Article
Full-text available
New research results on phenomena due to the existence of electronic resonance energy levels and hybridized states at impurities of transition elements in semiconductors are presented. The data show that the thermal conductivity and ultrasonic parameters of mercury selenide containing iron impurities have resonance anomalies due to the influence of...
Article
The temperature dependence of the phase velocity and absorption of ultrasound propagating along the [110] axis in a ZnSe crystal doped with Cr2+ ions is investigated in the frequency interval 32-158 MHz. It is found that the absorption peak and anomalies of the phase velocity observed in the temperature interval 10-20 K are of a relaxation nature....
Article
Ultrasonic investigations have been carried out in geometry of the experiment corresponding to acoustic analogy of the Faraday effect with the use of a super pure crystal like indium. Lowering the temperature from 4.2 K to 1.28 K has revealed new peculiarities of in the magnetic field dependences of absorption and phase velocity of circularly polar...
Article
Theory of ultrasonic absorption and dispersion, based on the Zener equation, was used for constructing the equations, those made it possible to restore the temperature dependences of relaxation time, adiabatic and isothermal elastic moduli on the basis of experimental data on the temperature dependences of ultrasound absorption and phase velocity....
Article
Temperature dependences of phase velocity and absorption of ultrasound were investigated in ZnSe crystal doped with Cr2+ ions at the frequencies 32–158 MHz. Absorption peak and variation of phase velocity found in the temperature interval 10–20 K were interpreted as manifestation of the Jahn-Teller effect. Temperature dependences of relaxation time...
Article
This paper reports on the results of temperature investigations into the absorption and velocity of ultrasound in ZnSe: Ni and ZnSe: Cr crystals in the frequency range 33–268 MHz. The frequency dependence of the absorption at the maximum is analyzed, and the energy of the excited state of the Ni2+ ions is calculated. The dynamic contribution to the...
Article
The peak of ultrasonic absorption observed at ≈13 K in ZnSe:Ni crystals with dopant concentration of 5.5 × 1019 cm–3 was interpreted as due to the Jahn–Teller effect. The dynamic contribution to the effective elastic modulus was accounted for and the temperature dependences of relaxation time, relaxed and unrelaxed modulus C44 were obtained. The pr...
Article
Magnetic field dependences of absorption and phase velocity of circularly polarized ultrasonic waves were studied in super pure crystal of indium at the temperatures 1.28–4.2 K. Geometry of experiment corresponded to acoustic analogy of the Faraday effect. Multiple doppleron-phonon resonances were observed, as well as sharp peaks of Doppler-shifted...
Article
Ultrasonic experiments on ZnSe and ZnSe:Ni crystals with impurity concentrations of 5.5×1019 cm−3 have revealed precursor phenomena at temperatures much higher than the temperature of the structural transition (Tc=14.5 K). It is found that the elastic constant C44 softens while C11 and C12 become stiffer as Tc is approached from above; the strains...
Article
The dispersion equation for doppleron-phonon modes was constructed and solved analytically in the strong coupling regime. The Fermi surface model proposed previously for calculating the doppleron spectrum in an indium crystal was used. It was shown that in the vicinity of doppleron-phonon resonance, the dispersion curves of coupled modes form a gap...
Article
The discovery of a low temperature structural transition in an ionic covalent crystal with a high degree of covalency was discussed. The structural transitions were found to be induced by a three dimensional impurity of an extremely low concentration. Experiments on elastic scattering of thermal neutrons were performed at a multi-detector diffracto...
Article
Ultrasonic experiments, done on ZnSe:Ni crystal with the dopant concentration 5.5×1019 cm−3, revealed precursor phenomenon in the form of lattice softening at temperatures significantly exceeding the temperature of structural transition (Tc=14.5 K). It proved to be that the order parameter of the transition was associated with the shear deformation...
Article
Upon reflection of a transverse linearly polarized ultrasonic wave from the interface between the fused quartz and single-crystal yttrium iron garnet, polarization changes dependent on the applied magnetic field H, such as conversion to elliptic polarization and rotation of the polarization plane, were revealed. The experiments were conducted at a...
Article
Absorption and phase velocity dispersion of circularly polarised ultrasonics are studied under DPR (doppleron-phonon resonance) conditions in tungsten. It is found experimentally that the magnetic field dependence of ultrasonic absorption on resonant polarisation is represented by an asymmetric peak, sometimes doublet, whereas the dependence of pha...
Article
Full-text available
Method for precise measurements of the ellipticity and rotation of the polarization of a transverse ultrasonic wave is presented. It is applicable for investigating the acoustic analogs of the Faraday, Cotton-Mouton, and Kerr effects. The technique consists of measuring amplitude of the voltage on the receiving piezoelectric transducer at a certain...
Article
Full-text available
Theory of the acoustic analog of the polar Kerr effect is developed for an inclined incidence of the p-type wave on the interface between isotropic non-magnetic medium and ferromagnetic cubic crystal. Magnetic field dependences of ellipticity and rotation of the polarization plane of the reflected wave under magnon-phonon resonance are analysed in...
Chapter
In the first three sections of this chapter we will develop a phenomenological or macroscopic theory for magnetoacoustic polarization phenomena. Model calculations for YIG are included to aid in the interpretation of the experimental results for magnetic materials presented in Chapter 5. In subsequent sections the quantum properties of the conducti...
Chapter
There are three principal types of ultrasonic installations that may be used for investigating MPP. Those based on amplitude or phase-amplitude measurements, discussed in the previous chapter, allow one to perform precise ultrasonic polarimetry, whereas another type, the ultrasonic field visualizer, gives qualitative data. The latter was developed...
Chapter
As mentioned in the Introduction, the first quantitative data on MPP were obtained in single crystals of YIG [9, 10]. The magnitudes of ε and ø in these experiments were large enough to allow them to be determined from the distortion of the exponential decay of the ultrasonic echo pulses as observed on an oscilloscope. This method for evaluation of...
Chapter
In 1960 Bömmel and Dransfeld reported the first observation of rotation of polarization in a ferromagnet [8]. They investigated the propagation of shear ultrasound through a thin disk of YIG magnetized in the hard direction near ferromagnetic resonance. In addition to strong absorption, the authors discovered that the polarization rotated about 45°...
Chapter
The rotation of the polarization and the ellipticity of ultrasound for DSCR are formally described with the aid of the wave vectors obtained in the weak-coupling approximation and given by equation (4.92). In this equation the electroacoustic coefficients should be written as functions of k 0 instead of k since the equation results from the first i...
Article
A technique for investigating magnetoacoustic phenomena such as the ultrasonic analogs of the Faraday, Cotton-Mouton, and Kerr effects is reported. This technique makes it possible to measure the ellipticity and the angle of rotation of the polarization plane of ultrasound. Measurements were made using data on amplitude and phase variations of the...
Article
Anomalously large oscillations of the ultrasonic absorption of shear circularly polarized waves have been discovered in a single crystal of superpure indium. By a number of features, the phenomenon can be interpreted as giant geometric oscillations, which have been predicted in [1].
Article
Quantum oscillations of ellipticity, rotation of the polarization plane of ultrasound initiated by the differences in magnetic field dependences in absorptions and phase velocities of circularly polarized ultrasonic waves are studied in a super pure single crystal of tungsten beyond the cyclotron absorption edge. A quantitative agreement has been o...
Article
Magnetoacoustic phenomena involving alteration of the polarization of a transverse wave (namely, the ultrasonic analogs of the Faraday and Cotton–Mouton effects) have been found in yttriumirongarnet [H. Matthews and R. C. LeCraw, Phys. Rev. Lett. 8, 397 (1962); B. Luthi, Phys. Lett. 3, 285 (1963)]. As the ellipticity E and the angle F of rotation o...
Article
In a longitudinal magnetic field, oscillations of the ultrasonic polarization parameters have been found for the propagation of shear waves along the tetragonal axis in superpure indium. A theoretical description has shown that the oscillations may be classified as a new phenomenon, which is conditioned, unlike the Pippard geometric oscillations, n...
Article
A detailed investigation of the recently disco vered magnetoacoustic oscillations of ellipticity has been undertaken in indium single crystals under the non-traditional mutual orientation of the magnetic field H and the ultrasound wave-vector q (close to H‖q). It has been found that oscillations appear in the field dependences of absorption and pha...
Article
For the case of strong bond between elastic and electromagnetic subsystems in metal, indium in particular, calculations were accomplished to determine dependences of ellipticity (ε) and angle of rotation of ultrasound polarization plane (Φ) on magnetic field (H) under conditions of helicon-phonon resonance. Calculation results were compared with ea...
Article
In a longitudinal magnetic field, oscillations of ellipticity have been found for the propagation of shear ultrasound along the tetragonal axis in superpure indium. A suggested interpretation is based on a theory of magnetoacoustic geometric oscillations taking into account the frequency dispersion.
Article
A device for observation of the character of transverse ultrasonic wave polarization after its transmission through an elastic-anisotropic sample is described. The device performs in the 107-109 Hz frequency range and is designed for studying into magnetoacoustic polarization effects (acoustic analogs of the Faraday and Cotton-Mouton magnetooptical...
Article
The temperature dependences of the elastic moduli (Youngs's and shear moduli) and internal friction are investigated in ceramic specimens La2-xSrxCuO4 (0.08 ≤x≤0.60). It is shown that lattice instability occurs in the superconductors of the La-Sr-Cu-O system, and is manifest either in the form of a structure transition (for specimens with x < 0.2)...
Article
In ceramic specimens La2-xSrxCuO4 (0.08≤x≤0.60) the temperature dependences of the velocity of ultrasound are investigated in the frequency range 50-100 kHz. Several normal modes are discovered, which resonate with one another in the temperature range of the structural transition. The experimental results are interpreted on the basis of the theory...