Mykola M. Krupa

Mykola M. Krupa
Institute of Magnetism (IMAG) NAS · Department of Physics of Magnetic Materials and Nanocrystalline Structures

Doctor of Physik, Pr.

About

105
Publications
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151
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Publications

Publications (105)
Chapter
Bilayers containing an interface between a thin layer of a heavy metal and a magnetic one are important hybrid materials in spintronics, as they combine magnetic order, strong spin–orbit interaction, and broken inversion symmetry.
Article
Dynamic properties of ferromagnetic nematic liquid crystals under an external magnetic field have investigated. The coupled dynamics of the magnetization, M, and the director field, n, associated with the liquid crystalline orientation order, have studied. In the framework of the hydrodynamicand and thermodynamic approach, the role of the dynamic c...
Chapter
Formation of the spin torque on the magnetization and the magnetization dynamics in multilayer magnetic nanostructures with metal nonmagnetic spacers have been studied. In a microscopic approach with spinor wave functions, the expansion of spin-polarized itinerant electrons across the system with spin-dependent interface scattering is considered fo...
Article
Magneto-induced molecular orientational transitions in nematic liquid crystals doped by ferromagnetic nanoparticles have studied. On the basis of a microscopic approach of tensor operators it is sequentially considered the influence of the ferromagnetic dopes on the sensitivity of the orientational structure and the optical activity of the nematic...
Chapter
The spin transport through and near interfaces have been studied in magnet/normal metal-based multilayer magnetic nanostructures in magnetostatic and magneto-dynamic cases. Its features and accompanying effects, such as the magnetoresistance or the magnetic precession-induced spin pumping and spin accumulation in adjacent normal metal, are determin...
Article
In tensor operator representation, the intermolecular potential and the total energy functional of nematic liquid crystals with elastic deformation and magnetic impurities has studied. The impact of the external field on the orientation molecular structure is considered as the variational problem of the energy functional minimum taking into account...
Conference Paper
Features of the current spin-orbit-induced magnetic dynamics in multilayer nanostructures with nonmagnetic heavy metal layers possessing a strong spin-orbit interaction are studied. These structures include ferromagnetic (FM) and antiferromagnetic (AF)/normal metal (NM) nanostructures based on both conductive and insulating magnetics and heavy norm...
Article
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The single-phase nanoscale Sr2FeMoO6-δ powders with various degrees P of superstructural ordering of Fe³⁺⁺and Mo⁵⁺⁺cations are obtained with the use of citrate-gel method at pH = 4, 6, 9 (P = 65% for pH = 4, P = 51% for pH = 6, and P = 20% for pH = 9). The sequence of phase transformations is studied, the temperature ranges of formation and dissolu...
Article
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In the present article we want to consider some features of not thermal influence of laser pulses on multilayer heterogeneous nanofilms to present the results of our experimental researches of change of the roughness of a surface and magnetic characteristics of permalloy films after their irradiation nanosecond laser pulses and the results of measu...
Article
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IN the present article we want to describe the main methods and schemes that are used in constructing spintronics elements and devices, and also give a brief analysis of the prospects for their introduction into practice. In our opinion, spintronics devices can replace microelectronic devices in some limited field of technology. First of all, this...
Article
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In the present article we want to consider some features of not thermal influence of laser pulses on multilayer heterogeneous nanofilms to present the results of our experimental researches of change of the roughness of a surface and magnetic characteristics of permalloy films after their irradiation nanosecond laser pulses and the results of measu...
Article
Full-text available
Abstract: In the present article we want to consider some features of not thermal influence of laser pulses on multilayer heterogeneous nanofilms to present the results of our experimental researches of change of the roughness of a surface and magnetic characteristics of permalloy films after their irradiation nanosecond laser pulses and the result...
Article
Full-text available
Features of the current and spin-orbit-coupling induced magnetic dynamics in multilayer nanostructures with nonmagnetic heavy-metal layers possessing by a strong spin-orbit coupling are studied. The spin Hall effect of the conversion of an incoming charge current into a transverse (with respect to the charge current) spin current impacting on the m...
Article
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The problem of creation of small size wideband sensitive sensors of magnetic field with a narrow directional diagram and a small coefficient of thermal drift is actual and requires searching for new magnetic materials. We present the results of the development of the flux-gate sensors with the 20 �m magnetic core of amorphous foils of ММ-3Cо and ММ...
Chapter
The electric-driven magnetization dynamics in multilayer magnetic nanostructures with strong spin–orbit coupling has been investigated. Controlled changes of magnetization occur via a spin polarization with conversation of the input charge current into the spin current, which coupled with the background magnetization by an exchange interaction. Gen...
Article
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Spectral ellipsometry technique is demonstrated to be a useful tool for the investigation of optical and magneto-optical parameters of magnetic heterostructures. Ellipsometry parameters  ,  were measured in the range of 350-1000 nm. Solving the inverse problem by a regression method the refractive index and thickness of the layers were deduced. M...
Data
The article presents the results of experimental studies of physical mechanisms and dynamics of magnetization reversal of the film Al2O3/Tb25Co5Fe70/Al2O3, Al2O3/Tb22Co5Fe73/Al2O3, Al2O3/Tb19Co5Fe76/Al2O3, Al2O3/Co30Fe70/Al2O3 with a single magnetic layer and the films Al2O3/Tb22Co5Fe73/Pr6O11/Tb19Co5Fe76/Al2O3, Al2O3/Co80Fe20/Pr6O11/Co30Fe70/Al2O3...
Article
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The field-induced impact on magnetic nanostructures with a large spin-orbit interaction, consisting in magnetization reversal under ultra-short circularly polarized laser pulses or unipolar electric field pulses are studied. Using the magneto-optical method and a pump-probe technique based on the Kerr and Faraday effects, we have established featur...
Chapter
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We have studied the mechanisms of a pulsed laser impact on the magnetization configuration in ferrimagnetic multilayered magnetic nanostructures, specifically, tunneling magnetic junctions taking into account laser-induced kinetic effects. The mechanism of such laser-induced impact is a complex process of laser-induced thermal demagnetization of ma...
Patent
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Article
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The paper presents the results of experimental studies of the physical mechanisms and dynamics of magnetization reversal of the films Al2O3/Tb25Co5Fe70/Al2O3, Al2O3/Tb22Co5Fe73/Al2O3, Al2O3/Tb19Co5Fe76/Al2O3, Al2O3/Co30Fe70/Al2O3 with a single magnetic layer and the films Al2O3/Tb22Co5Fe73/Pr6O11/Tb19Co5Fe76/Al2O3, Al2O3/Co80Fe20/Pr6O11/Co30Fe70/Al...
Book
Full-text available
Today, features of the interaction of laser radiation with matter have searched out the wide application in several fields of science and technique. Specifically, corresponding effects effectively use in the magneto-optical spectroscopy with high spatial and time resolution and for controlling of magnetic states in nanostructures. The highly cohere...
Article
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In this paper, we present study of the measurement peculiarities of magnetic Fe3O4 and NiFe2O4 nanoparticles characteristics. The nanoparticles possess ferromagnetic properties. The aim of the work was to determine the magnetic parameters of such nanoparticles and to investigate influence of magnetic field and interaction between individual nanopar...
Article
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The article presents the results of experimental studies of physical mechanisms and dynamics of magnetization reversal of the film Al 2 O 3 /Tb 25 Co with a single magnetic layer and the films Al 2 O 3 /Tb 22 Co 5 Fe 73 /Pr 6 O 11 /Tb 19 Co 5 Fe 76 /Al 2 O 3 , Al 2 O 3 /Co 80 Fe 20 /Pr 6 O 11 /Co 30 Fe 70 /Al 2 O 3 with two magnetic layers radiated...
Article
The laser-induced magnetic after-effects in magnetic nanostructures consisting in magnet reversal under ultra-short circularly polarized laser pulses are studied. Using the magneto-optical method and a pump-probe technique based on the Kerr and Faraday effects, features and conditions of magnetic reversal in ferrimagnetic-based nanostructures under...
Article
Full-text available
Spectral ellipsometry technique is demonstrated to be a useful tool for the investigation of optical and magneto-optical parameters of magnetic heterostructures. Ellipsometry parameters ψ, Δ were measured in the range of 350-1000 nm. Solving the inverse problem by a regression method the refractive index and thickness of the layers were deduced. Ma...
Article
Full-text available
Spintronic belongs to one of the most the quickly developing area of science and technology, which is based on the control over the processes of transfer of spin current among the elements of electronic devices. To create high-spintronics, elements necessary reversing control the magnetic electrodes with high speed. Interestingly, the possibility o...
Article
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We use the self-generation method to study conductivity and temperature of the martensitic transition in the films of Ni52Mn24Ga24 and Ni49.5Mn28Ga22.5. The scheme of self-oscillator construction on the martensitic transition in a Ni49.5Mn28Ga22.5 film is described, and the influence of the magnetic field on the operation of such a generator is stu...
Article
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In this work, we suggest the temperature-induced resistivity change at the martensitic transformation in the Ni-Mn-Ga ferromagnetic shape memory alloy as a driving mechanism enabling periodic signal generation. We demonstrated its practical importance by a design of the prototype of a low-frequency autonomous generator. A prominent feature of this...
Article
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The article focuses on photon drag effect under laser radiation in solid state materials. This effect causes a high concentration of nonequilibrium electrons in the area of the laser beam the exit out of material. Coulomb interaction of spatial charge of these electrons with the charged impurity atoms can cause their drift in the direction of laser...
Article
Full-text available
We have studied the mechanisms of a pulsed laser impact on the magnetization configuration in ferrimagnetic multilayered magnetic nanostructures, specifically, tunneling magnetic junctions. The mechanism of such the laser-induced impact is a complex process of laser-induced thermal demagnetization of magnetic sublattices with subsequent biasing by...
Article
Full-text available
We have studied the laser-induced high-speed remagnetization and tunneling magnetoresistance (TMR) effects in tunnel magnetic junctions (TMJ). Using magneto-optical investigations, all-optical pump and probe technique, we have studied mechanisms of the laser-induced remagnetization and shown feasibility of the high-speed laser-controlled remagnetiz...
Article
Full-text available
1. INTRODUCTION Spintronics belongs to one of the most quickly developing areas of science and technology, it is based on the control of the processes of transfer of spin current between the elements of electronic devices. Researches of a spin dependent transport and spin relaxation in solids, search for new materials with the high degree of an ele...
Article
Full-text available
Physical mechanisms of magnetization reversal of multilayer magnetic nanofilms by laser radiation are examined and the experiments on the effect of the magnetic field and nanosecond and picosecond laser pulses on the conductivity of the Tb19Co5Fe76/Pr6O11/Tb22Co5Fe73 and Co80Fe20/Pr6O11/Co30Fe70 tunnel microcontacts are carried out. It is shown tha...
Article
This paper presents the results of experimental studies of both the magnetic reversal of Tb(19)Co(5)Fe(76)/Pr(6)O(11)/Tb(22)Co(5)Fe(73) and Co(80)Fe(20)/Pr(6)O(11)/Co(36)Fe(70) nanofilms and the conductivity switching in tunnelling microcontacts obtained on the base of these films irradiated by nanosecond and picosecond laser pulses. These results...
Article
Full-text available
It is determined that the state of initial reagents considerably influence the inhomogeneity of Sr2FeMoO6-δ samples microstructure which has caused the appearance of super-paramagnetism and spin glass state in Sr2FeMoO6-δ.
Article
Results of experimental investigations of laser radiation interaction with the Ti, Co, NiFe, TbFe and LaSrMnO3 films are presented. It is shown, that it is possible to improve magnetic characteristics and to obtain magnetic films with regular distribution of nanodots by the laser radiation. It is observed an increasing of magnetic permeability and...
Article
Full-text available
The results of investigation of magnetization reversal dynamics of ferrimagnetic amorphous nanolayers with transverse anisotropy is investigated for Al{sub 2}O{sub 3}/Tb{sub 22}Co{sub 5}Fe{sub 73}/Al{sub 2}O{sub 3} and Al{sub 2}O{sub 3}/Tb{sub 22}Co{sub 5}Fe{sub 73}/Pr{sub 6}O{sub 11}/Tb{sub 19}Co{sub 5}Fe{sub 76}/Al{sub 2}O{sub 3} multilayer films...
Article
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We study experimentally the radiation from cadmium sulfide monocrystal wafers 0.02–0.25 mm thick grown from gas phase and excited by nanosecond laser pulses. It is shown that along with the luminescence in the visible range, which is related to the exciton–exciton scattering process, terahertz radiation, which can be related to transitions in the e...
Article
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Experimental studies of the emission of thin CdS single crystals upon excitation with a nitrogen laser and a second harmonic of a neodymium laser are carried out. It is shown that along with the luminescence in the visible region, which is associated with the exciton-exciton scattering process, at temperatures of 300 K and 77 K, radiation is observ...
Article
Changes in magnetic states of film magnetic nanostructures based on the TbCoFe compounds under pulse polarized laser radiation are investigated. As shown, the decrease of pulse duration of the circularly polarized laser radiation from nano- to picosecond intervals results in increase of the direct (nonthermal) laser impact on the magnetic states of...
Article
The influence of grain sizes of SrFeO3 and SrMoO4 precursors on phase transitions sequence, and Fe3+and Mo5+ cations ordering in Sr2FeMoO6-delta is investigated.
Article
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The experimental results of the investigation of tunneling magnetoresistance (TMR) in TbCoFe/Pr6O11/TbCoFe films at temperatures of 80 and 300 K are presented. The resistance of the structure increases by more than a factor of 1.5 at room temperature and by more than a factor of 3 at a temperature of 80 K under the transition from the state with th...
Article
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The results of experimental studies of the recording characteristics of information by laser radiation in thin films of a phthalocyanine dye with bismuth are presented. It is shown that the drift of bismuth atoms is observed in three-layer dye-bismuth-dye films under the action of nanosecond laser pulses, which is associated with the electrostatic...
Article
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The influence of nanosecond laser impulse irradiation on the magneto-optical properties of multilayer film nanostructures Bi-SiC-TbFe-SiC, SiC-TbFe-SiC, SiC-Tb-Au-Fe-SiC, and phthalocyanine dye-bismuth-phthalocyanine dye was investigated. It was shown that this irradiation causes the injection of spin-polarized electrons from magnetic into nonmagne...
Article
An investigation was made of the nature and magnitude of the threshold of damage caused by ruby and neodymium laser radiation to CdSxSe1–x and ZnxCd1–xS semiconductors with a range of forbidden band widths. Surface and bulk damage was observed depending on the ratio of the forbidden band width to the laser photon energy. The surface damage involved...
Article
An investigation was made of the photoconductivity of pure CdS crystals at the moment of appearance of bulk damage and of the kinetics of this damage. An analysis of the experimental data revealed direct multiplication of carriers as a result of bulk damage, dependence of the bulk damage threshold on the amplitude of the optical wave field, and the...
Article
Dynamic holographic recording and erasure was investigated for the first time in a new class of mixed ZnSe)x–(GaP)1–x semiconductor crystals. At high excitation rates the Auger recombination process became important and it limited seriously the diffraction efficiency of nonequilibrium-carrier holograms. This process and the absorption of light by f...
Article
Full-text available
The effect of nanosecond laser pulses with λ = 355 nm on the Kerr and Faraday angles in nanosize layered magnetic films Al2O3/TbFe/Al2O3/TbFe/Al2O3 and Al2O3/TbFe/Au/TbFe/Al2O3 is studied experimentally. The first ferrimagnetic TbFe layer in these films with transverse anisotropy is enriched by terbium, while the second Tb22Fe78 layer is enriched b...
Article
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The underlying physics of the giant magnetic or mechanical field-induced-strains in Ni-Mn-Ga alloys are briefly discussed. For the purpose of illustrating some fundamental aspects, experimental data relative to lattice instability and composition dependence of magnetization are presented alongside reported results. An implementation of Ni-Mn-Ga sin...
Article
Full-text available
The effect of nanosecond laser pulses on the optical and magnetic properties of Bi-SiC-TbFe-SiC, SiC-TbFe-SiC, SiC-Tb-Au-Fe-SiC, and phthalocyanine dye-bismuth-phthalocyanine dye multilayer nanofilms is experimentally studied. The photon pressure of a laser beam is shown to cause electrons to drift in the direction of beam propagation. As a result...
Article
Full-text available
We report on the results of experimental studies of the characteristics of record of information by laser radiation in thin films of a phthalocyanine dye with bismuth. It is shown that bismuth atoms drift in dye-bismuth-dye triplex films under the action of nanosecond laser pulses. This effect is due to the electrostatic interaction between the bis...
Article
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Results of experimental investigations of interaction of laser radiation with films of Ti, Co, NiFe, TbFe, and LaSrMnO(3), are presented. As shown by means of laser radiation, it is possible to improve the magnetic characteristics and to obtain the magnetic films with regularly distributed nanoislands. After an irradiation of NiFe films by nanoseco...
Article
Full-text available
We experimentally study the influence of the laser-induced drift (LID) of dopant electrons and atoms on the optical properties of semiconductors. It is shown that the LID of electrons results in a dramatic change in the refractive index in the region of laser-radiation output from semiconductor crystals, impairement of the total internal reflection...
Article
The injection of spin-polarized electrons in nanofilms Bi-SiC-TbFe-Si and Ti-SiC-TbFe-Si under action of a powerful laser radiation is experimentally registered. Such electrons are injected by the radiation from the ferrimagnetic-TbFe layer with a perpendicular anisotropy in Bi or Ti layers. It results in increase of the angle of the rotation of li...
Article
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The results are presented of experimental studies of variations in the polarization of light reflected from multilayer thin metal films containing nonmagnetic Bi or Ti films and a TbFe magnetic film magnetized in the direction perpendicular to the film plane. An additional optical rotation of light reflected from bismuth and titanium films was obse...
Article
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We demonstrate the possibility of constructing nonkinematic data-recording devices based on a special optical board with planar electrooptical lightguides and ultrasonic-signal storing in highly dispersed magnetic-striction polycrystalline ferrites. The efficiency of operation of planar electrooptical light guides made of cadmium sulfide and galliu...
Article
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This paper describes a method of separating out individual picosecond pulses from a train of self-synchronized laser pulses by means of a nonlinear spatial filter. This filter is based on the nonlinear lenses that an formed by the refractive-index variation of semiconductors in a powerful laser-radiation held. The features of nonlinear lenses in an...
Article
Investigation of different technology-factor influence on physical and technical characteristics of TbFe films are carried out It is shown that perpendicular anisotropy in such films is strong dependent on the Tb and Pe concentrations and is increasing with a sputtering rate. A substitution of Fe atoms by Co atoms makes better the characteristics o...
Article
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Methods for increasing the signal-to-noise ratio in magneto-optical data recording heads due to compensation background component with special diaphragms and polarization compensators, as well as when introducing into the head rotators of the plane polarization. Design and technical features are considered small quartz and ferite-garnet rotators
Article
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This paper describes methods of enhancing the SNR in magnetooptic information-recording heads by attenuating the background component with special stops and polarization compensators, as well as by introducing rotators of the plane of polarization into the head. The design and technical features of compact quartz and ferrogarnet rotators are consid...
Article
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The light-induced drift of electrons, light-absorbing impurities, and defects in II-VI semiconductors is investigated experimentally, along with some potential practical applications of the phenomenon. It is shown that the light-induced drift of electrons induces a very pronounced change in the refractive index, |Δn|∼0.01, and can be used to implem...
Article
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This paper describes the technology and optomechanical setup for production of a high-strength contrast submicron phase structure on the surface of an optical element by the technique of laser cutting of a deposited silicon carbide film. When using an argon laser and focusing microlens with numerical aperture NA=0.65, the minimum size of individual...
Article
Methods are proposed for cancelling the depolarization background which arises from inhomogeneities in the polarization structure of a linearly polarized laser beam which has passed through the focusing-optics elements of a magnetooptic memory. The angles of the compensating rotation of the analyzer and the shapes of the pattern diaphragms are dete...
Article
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Irreversible structural changes in cadmium sulfide crystals, caused by laser radiation with quantum energy insufficient to excite electron transitions of the band-band or band-impurity type, were studied. From an investigation of the low-temperature luminescence spectra, it was established that continuous infrared illumination (10. 6 mu ) causes ac...
Article
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1. In the field of laser radiation in semiconductors, the drift of electrons and atomic impurities occurs, which affects the optical characteristics and the nature of the interaction of laser radiation with semiconductors. 2. LID of electrons in the field of nanosecond and picosecond laser pulses causes a record high magnitude of the refractive ind...
Article
Processes of dynamic holographic recording and erasing in a new class of /ZnSe/x-/GaP/1-x mixed semiconductor crystals are analyzed. Auger recombination processes are shown to become important under high levels of semiconductor excitation. These processes limit the diffraction activity of nonequilibrium-carrier holograms. Bibtex entry for this abst...