Aa Galkin Donetsk Physico Technical Institute

Donets’k, Ukraine

Aa Galkin Donetsk Physico Technical Institute

Donets’k, Ukraine
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Prokhorov A.A.,ASCR Institute of Physics Prague | Chernush L.F.,Aa Galkin Donetsk Physico Technical Institute | Babin V.,ASCR Institute of Physics Prague | Buryi M.,ASCR Institute of Physics Prague | And 4 more authors.
Optical Materials | Year: 2017

We have studied the X-ray irradiated EuAl3(BO3)4 single crystals by means of luminescence and electron paramagnetic resonance (EPR) spectroscopy. It was found that the X-ray irradiation modifies the color of the EuAl3(BO3)4 crystal and leads to the formation of a stable Eu2+ centers from the Eu3+ centers located in a host matrix. Annealing of the crystal at 600 °C leads to the restoration of the original color and the disappearance of Eu2+ centers. The EPR and luminescence spectra of the Eu2+ ion were studied in a wide temperature range. The angular dependence of Eu2+ EPR spectra is described by an axial spin Hamiltonian characterized by the spin of S = 7/2 with the following parameters: gz = gx = 1.991 (1); b2 0 = −267,86 (16)*10−4cm−1; b4 0 = −4,20 (8)* 10−4cm−1; b6 0 = 0,37 (13)* 10−4cm−1; A (151) = 31,4 (3)* 10−4cm−1; A (153) = 13,9 (3)* 10−4cm−1. Based on the comparison of spin Hamiltonian parameters of Eu2+ and Gd3+ ions, it was concluded that Eu2+ ion located at the Eu3+ site in the EuAl3(BO3)4 crystal lattice. Within the framework of the superposition model, the distortions introduced to the local environment by the Eu2+ and Gd3+ ions were analyzed. In the luminescence spectra, the bands associated with the Eu2+ and Eu3+ ions are detected. The photoluminescence decay kinetics of Eu3+-related emission (614 nm) has a single-exponential character, whereas the Eu2+-related band (323 nm) possess more complicated decay kinetics behavior that may point to the Eu2+ excited state ionization and its delayed recombination. © 2017 Elsevier B.V.


Prokhorov A.A.,ASCR Institute of Physics Prague | Chernush L.F.,Aa Galkin Donetsk Physico Technical Institute | Dyakonov V.P.,Polish Academy of Sciences | Szymczak H.,Polish Academy of Sciences | Prokhorov A.D.,Aa Galkin Donetsk Physico Technical Institute
Journal of Magnetism and Magnetic Materials | Year: 2016

New data on the ground state of impurity Ru3+ ions in the crystals of YAl3(BO3)4 and EuAl3(BO3)4 aluminum borates were obtained. It was shown that Ru3+ ion replaces trivalent rare-earth ions without breaking the symmetry of the site. The crystal field acting on 4d5 ions forms an EPR spectrum, which is described by the spin Hamiltonian with S=1/2. The spin-Hamiltonian parameters determined are equal to gII=1.963, g⊥=3.796, AII=43.03*10−4 cm−1, A⊥=84.86*10−4 cm−1 in the YAl3(BO3)4 crystal (at Т=15 K) and gII=2.016, g⊥=3.796 in the EuAl3(BO3)4 crystal (at Т=15 K). It is found that the value of ∆g=gII-g⊥ is an indicator of distortions of nearest environment of Ru3+ ion. The angle between the C3 axis and the direction into nearest oxygen ion was determined. The EPR linewidth of Ru3+ ion increases with increasing temperature due to the dipole-dipole and exchange interactions with the excited states of the host lattice Ru3+ ion. © 2016 Elsevier B.V.


Dyakonov V.,Polish Academy of Sciences | Dyakonov V.,Aa Galkin Donetsk Physico Technical Institute | Dyakonov V.,Jagiellonian University | SzytuLa A.,Jagiellonian University | And 8 more authors.
Acta Physica Polonica A | Year: 2010

We report on the X-ray powder diffraction and magnetic measurements of the polycrystalline and the two nanocrystalline samples of DyMnO3 compound synthesized at temperatures of 800 and 850 °C. All samples at room temperature crystallize in the orthorhombic crystal structure (space group Pnma). The crystal structure parameters determined change only slightly with preparation methods but the average grains size of the nanoparticles determined from X-ray data increases significantly with increasing annealing temperature. Temperature dependence of the magnetic susceptibility indicates the antiferromagnetic order in Dy sublattice at low temperatures.


Dyakonov V.,Polish Academy of Sciences | Dyakonov V.,Aa Galkin Donetsk Physico Technical Institute | Slawska-Waniewska A.,Polish Academy of Sciences | Nedelko N.,Polish Academy of Sciences | And 13 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2010

X-ray powder diffraction, magnetization, transport and magnetic resonance measurements of nanosize La0.7Sr0.3MnO3 (LCMO) manganites have been performed. The nanosize manganites were synthesized with a co-precipitation method at different (600, 700, 800 and 1000 °C) temperatures. The crystal structure of the nanopowders obtained was determined to be perovskite-like with a rhombohedral distortion (the space group R3̄c). The average size of synthesized nanoparticles (from 17 to 88 nm) was estimated using the X-ray diffraction and low temperature adsorption of argon methods. All the nanosize manganites show ferromagnetic-like ordering. Both the Curie temperature and magnetization decrease with reducing the particle size. The decrease of magnetization is due to the disordered surface shell of particles. The disordered surface layer is a source of the surface anisotropy and is responsible for the increase of coercivity. Temperature dependences of the magnetic resonance spectra parameters have allowed obtaining information on dynamics of magnetic properties in the nanoparticle systems. The resistivity was established to become higher by reducing the particles' size and increases to a great extent in nanoparticles with the smallest average size at low temperatures. The magnetic entropy was shown to be smaller for the small particles. Using the temperature dependence of magnetic entropy the relative cooling power of the nanosize samples studied was evaluated. © 2010 Elsevier B.V.


Prokhorov A.D.,Aa Galkin Donetsk Physico Technical Institute | Prokhorov A.A.,Aa Galkin Donetsk Physico Technical Institute | Chernush L.F.,Aa Galkin Donetsk Physico Technical Institute | Minyakaev R.,Polish Academy of Sciences | And 3 more authors.
Physica Status Solidi (B) Basic Research | Year: 2014

The EPR spectra of Gd3+ ion replacing Y3+ or rare-earth (RE) ions in aluminum borates REAl3(BO3)4 (RE=Y3+, Eu3+, Tm3+) have been studied. The spin-Hamiltonian parameters of an impurity Gd3+ ion in these crystals were determined. The basic atom coordinates in the structure of TmAl 3 (BO3)4 crystal have been established. Distortions of the Gd3+ ion nearest environment were analyzed within the framework of the superposition model of zero-field splitting. The b20 parameter change in isomorphic aluminum borates is shown to be determined by change of the angle between the Gd3+-O2- bond and the C3-axis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Prokhorov A.D.,Aa Galkin Donetsk Physico Technical Institute | Prokhorov A.A.,Aa Galkin Donetsk Physico Technical Institute | Chernysh L.F.,Aa Galkin Donetsk Physico Technical Institute | Dyakonov V.P.,Aa Galkin Donetsk Physico Technical Institute | And 2 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2011

The ground state of Gd3 ions substituting for trivalent europium in the EuAl3(BO3)4 single crystal was studied by electron paramagnetic resonance (EPR) over the temperature range of 3004.2 K and at pressures up to 9 kbar. The EPR spectra were analysed using the spin Hamiltonian of axial symmetry. The following parameters are reported: g=1.981±0.002, b2 0=280.18±0.12, b 4 0=-12.95±0.08 and b6 0=0.61±0.12 (at T=298 K). The distortions of the nearest environment of Gd3 ion were analysed within the framework of the superposition model of crystal field. © 2011 Published by Elsevier B.V.


Bazela W.,Cracow University of Technology | Dul M.,Cracow University of Technology | Dyakonov V.,Polish Academy of Sciences | Dyakonov V.,Aa Galkin Donetsk Physico Technical Institute | And 8 more authors.
Acta Physica Polonica A | Year: 2012

The magnetic properties including magnetic structure of poly and nano samples of TbMnO 3 are determined. All the samples investigated are antiferromagnets. In these samples the Mn ad Tb moments order antiferromag-netically at different temperatures and form modulated magnetic structure described by the propagation vector κ=(κ x,0,0) with different value of κ x for the Mn and Tb sublattices. Comparison of the data for poly and nano samples indicates the decrease of the moment and increase of the κ x component of propagation vector in the nano specimens. The wide Bragg peak related to the Tb sublattice suggests that the magnetic order has the claster-like character. The magnetic moments value in both sublattices is smaller, whereas the κ x values are larger for nano samples.


Szytula A.,Jagiellonian University | Penca B.,Jagiellonian University | Dyakonov V.,Polish Academy of Sciences | Dyakonov V.,Aa Galkin Donetsk Physico Technical Institute | And 2 more authors.
Acta Physica Polonica A | Year: 2014

The neutron powder diffraction (NPD) measurements of the nano-size DyMnO3 manganite have been performed. The obtained results indicate that this compound crystallizes in the orthorhombic crystal structure described by the space group Pnma. The Mn and Dy moments order antiferromagnetically at different temperatures and form modulated magnetic structure described by the propagation vector κ = (κx; 0; 0) with the different values of κx component for the Mn and Dy sublattices. The values of κx component for Mn sublattice increase with decreasing of the temperature and are smaller that in bulk compound. The wide Bragg peaks related to the Dy sublattice suggest that the magnetic order in this sublattice has the cluster-like character.


Stognij A.,Scientific Practical Materials Research Center of Belarus | Novitskii N.,Scientific Practical Materials Research Center of Belarus | Sazanovich A.,Polish Academy of Sciences | Poddubnaya N.,Scientific Practical Materials Research Center of Belarus | And 6 more authors.
EPJ Applied Physics | Year: 2013

Magnetoelectric properties of layered heterostructures (FM/PZT/FM) n (n≤3) obtained by ion-beam sputtering deposition of ferromagnetic metal (FM), where FM is the cobalt (Co) or permalloy Ni 78Fe22, onto ferroelectric ceramic based on lead zirconate titanate (PZT) have been studied. The polished ferroelectric plates in thickness from 400 to 20 Im were subjected to finished treatment by ion-beam sputtering. After plasma activation they were covered by the ferromagnetic films from 1 to 6 Im in thickness. Enhanced characteristics of these structures were reached by means of both the thickness optimization of ferroelectric and ferromagnetic layers and obtaining of ferromagnetic/ferroelectric interfaces being free from defects and foreign impurities. Assuming on the basis of analysis of elastic stresses in the ferromagnetic film that the magnetoelectric effect forms within ferromagnetic/ferroelectric interface, the structures with 2a3 ferromagnetic layers were obtained. In layered heterostructure (Py/PZT/Py)3, the optimal thickness of ferromagnetic film was 2 Im, and outer and inner ferroelectric layers had 20 Im and 80 Im in thickness, respectively. For such structure the maximal magnetoelectric voltage coefficient of 250 mV/(cm Oe) was reached at a frequency 100 Hz in magnetic field of 0.25 T at room temperature. The structures studied can serve as energy-independent elements detecting the change of magnetic or electric fields in electronic devices based on magnetoelectric effect. © EDP Sciences, 2013.


Sazanovich A.,Polish Academy of Sciences | Pietosa J.,Polish Academy of Sciences | Pashchenko A.,Aa Galkin Donetsk Physico Technical Institute | Zubov E.,Aa Galkin Donetsk Physico Technical Institute | And 3 more authors.
Acta Physica Polonica A | Year: 2012

Magnetocaloric effect in (La0.7Ca0.3) 1-xMn1+xO3 manganites with x = 0, 0.1, 0.2 has been investigated. It is found a strong influence of nonstoichiometry caused by excessive manganese on the magnetic entropy change. The magnetocaloric effect was evaluated from the isothermal curves of spontaneous magnetization versus the applied magnetic field by using the well-known thermodynamical Maxwell relation. The maximum entropy value, ΔSmax M, near the ferromagnetic-paramagnetic phase transition is shown to increase with the manganese content. The La0.56Ca0.24Mn1.2O 3 manganite exhibits the largest ΔSmax M value equal to 3.09 J kg-1 K-1 at 15 kOe near T C = 267 K. The magnetocaloric effect values obtained allow to propose that the studied manganites are promising materials for future cooling application.

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