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1
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EPR in Kagome Staircase Compound Mg_{2.997}Co_{0.003}V_2O_8

100%
Aleshkevych P., Fink-Finowicki J.
Acta Physica Polonica A
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2007
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vol. 111
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issue 1
105-110
EN
The paramagnetic resonance of Co^{2+} ions in Mg_{2.997}Co_{0.003}V_2O_8 single crystals are reported. The EPR spectrum shows two groups of resonance lines associated with two crystallographically nonequivalent Co ions positions that are known in the kagome staircase system as "cross-tie" and "spine" sites. No preferential occupation of Co^{2+} ions in the kagome lattice was observed. The ground state was described by spin-Hamiltonian with an effective electronic spin S=1/2 and nuclear spin I=7/2. The local symmetry of oxygen octahedron surrounding Co ions, main values of the g-factors, and hyperfine structure were determined for both cobalt positions.
2
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High Quality (100) and (001) Oriented Substrates Prepared from Czochralski Grown SrLaGaO_{4} and SrLaAlO_{4} Single Crystals

81%
Berkowski M., Fink-Finowicki J., Sass J., Mazur K.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
201-204
EN
The growth of SrLaGaO_{4} and SrLaAlO_{4} crystals on ⟨100⟩ and ⟨001⟩ oriented seeds was investigated. Various defects, which appeared in crystals grown on these two orientations, were observed in polarized light and by X-ray diffraction topography. It was found that to obtain a substrate of the best quality, the crystal should be cut along the growth directions. Therefore, crystals pulled along ⟨100⟩ direction are utilized for preparation of (001) substrates, whereas (100) substrates are better to cut from crystals grown on ⟨001⟩ seed. The quality of the prepared substrates was determined by high resolution X-ray diffraction study in terms of rocking curve and mean mosaic angle.
3
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Defects in Detwinned LaGaO_{3} Substrates

81%
Mazur K., Fink-Finowicki J., Berkowski M., Schell N.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
205-208
EN
Single crystals of lanthanum gallate would be the suitable substrate for YBaCuO films except for the phase transition and the tendency to twinning existing in this material. However, by appropriate choice of growth conditions in the Czochralski method, it is possible to grow single crystal of LaGaO_{3} with low density of twin boundaries. Special stress and temperature treatment can then be applied to such materials to remove majority of existing twins. The substrates were examined by X-ray topography before and after detwinning and the surface was scanned with a profilometer.
4
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Role of Crystal-Melt Interface and Surface Tension on Czochralski Growth of Substrate Materials with K_{2}NiF_{4} Structure

81%
Berkowski M., Fink-Finowicki J., Gutowski M.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
197-200
EN
Crystal-melt interface was investigated during Czochralski growth of SrLaGaO_{4} and SrLaAlO_{4} crystals on ⟨001⟩ oriented seeds. Relations between the ratio of the core diameter, grown on (001) plane, and the crystal diameter, as a function of seed rotation speed were determined. It was confirmed that it is possible to control the core diameter during the crystal growth. A new module was introduced into the crystal growth controlling program. It enables to estimate the surface tension coefficient between crystal and melt at the beginning of crystallization. This value is then used to compute proper corrections for automatic weighting system.
5
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SrLaGaO_{4}-SrLaAlO_{4} Solid Solutions - Substrate Materials with Tuneable Lattice Parameter for Various HTSC Compounds

81%
Berkowski M., Fink-Finowicki J., Mojaiskaia E.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
182-186
EN
The increase in Τ_{c} for high temperature superconductors can be realized, among others, by appropriate substrate/film combinations. SrLaGaO_{4}-SrLaΑlO_{4} solid solutions were grown by the Czochralski method. The already achieved results allow to obtain single crystals of SrLaΑl_{1-x}Ga_{x}O_{4} with lattice constant a in the range from 0.3754 to 0.3775 nm, and SrLaGa_{1-x}Αl_{x}O_{4} crystals with lattice constant a in the range from 0.3843 to 0.3826 nm. Electron-probe microanalysis along obtained single crystals was used for determination of segregation coefficient between aluminum and gallium ions.
6
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Ellipsometric Studies of NdMnO_3 Single Crystals

62%
Babonas G., Reza A., Szymczak R., Baran M., Shiryaev S., Fink-Finowicki J., Szymczak H.
Acta Physica Polonica A
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2004
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vol. 105
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issue 1-2
197-208
EN
Ellipsometric studies of NdMnO_3 single crystals of orthorhombic symmetry were carried out in the spectral range 0.5-5.0 eV. Experimental data, which were obtained on the (001)_{pc}-type planes of pseudo-cubic system, were analyzed in the model of biaxial crystal. For the first time, three componentsε_x,ε_y,ε_z of the effective dielectric function for manganites of orthorhombic symmetry were determined. From ellipsometric data, the spectra of optical conductivity and loss function were also calculated and considered. The fine structure of the spectra and optical anisotropy was the basis for discussion of the microscopic origin of the optical transitions responsible for the optical features. The electronic excitations due to dipole-forbidden spin-allowed transitions of the d-d-type in Mn-ions, f-f-type in Nd-ions and charge-transfer 2p(O)-3d(Mn) transitions were taken into account. The data for NdMnO_3 were compared with those obtained for other related undoped and doped single crystals of perovskite-type structure, LaMnO_3, (LaBa)(MnCo)O_3 and (LaCa)CoO_3.
7
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Solid Solutions of Oxide Crystals as Substrates for Epitaxial Layer Depositions

62%
Berkowski M., Fink-Finowicki J., Aleksijko R., Diduszko R., Byszewski P., Kikalejshvili-Domukhovska R.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
457-463
EN
We present results of investigation on growth of solid solution crystals with perovskites and K_2NiF_4 structures used as substrates for epitaxy. Perovskite single crystals with no twins and crystals with K_2NiF_4 structure with the lattice parameter in the range 3.876-3.819Å and 3.754 to 3.688Å, respectively, can be grown. Here preliminary results on investigation on growth of other solid solution crystals with the lattice constant from 3.946 to 3.688Å are also presented thus covering the whole interesting range for depositing oxide materials. These crystals can be grown by the Czochralski method that secures their high structural quality. Discussed crystals are resistant to reaction with the deposited oxide layers.
8
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Anisotropic Magnetic Susceptibility of Neodymium Substituted SrLaAlO_{4} Crystals

62%
Fink-Finowicki J., Puźniak R., Baran M., Jabłoński R., Berkowski M., Pajączkowska A., Szymczak H.
Acta Physica Polonica A
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1994
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vol. 85
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issue 3
633-637
EN
The uniaxial anisotropy of magnetic properties of SrLa_{1-x}Nd_{x}AlO_{4} single crystals (x = 0.01 and 0.05) was found from the measurements of temperature dependencies of magnetic susceptibility. Results of measurements, with magnetic field along a- and c-axis, are compared with the similar data obtained for CaNdAlO_{4} crystal. The successful description of experimental data was done in frames of the crystal field approximation. The anisotropy of magnetic susceptibility appears due to crystal field acting on magnetic neodymium ions in a system without exchange interactions.
9
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Effect of Chemical Disorder on Geometrically Frustrated Kagome Lattice

62%
Szymczak H., Szymczak R., Baran M., Fink-Finowicki J., Krzymanska B., Aleshkevych P., Jezierski A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 1
35-42
EN
This paper reviews recent progress in the studies of magnetic dilutions on magnetic properties of two frustrated systems: magnetoplumbite-like SrGa_{12-x}Cr_xO_{19} and kagome staircase Co_3V_2O_8 doped with Mg ions. In the first group of compounds magnetic properties are determined by magnetic defects arising due to doping. In the case of kagome staircase compounds magnetic dilution suppresses effects of crystal field acting on magnetic ions. In particular, the dilution decreases magnetocrystalline anisotropy and anisotropy of magnetization.
10
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Structure and Superconductivity of FeSe_{1 - x} and FeTe_{1 - y}Se_{y} Crystals: Dependence on the Synthesis Methods, Starting Composition, and Growth Conditions

62%
Gawryluk D., Fink-Finowicki J., Wiśniewski A., Puźniak R., Domukhovski V., Diduszko R., Berkowski M.
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issue 2
331-335
EN
Syntheses of superconducting iron chalcogenides FeSe_{1 - x} (x = 0-0.15) and FeTe_{1 - y}Se_{y} (y = 0.3-0.55) were performed. Superconducting phase of iron selenide was obtained by the solid-state reaction and from liquid phase. The highest values of critical temperature (T_c = 8.2-8.7 K) exhibit FeSe_{1-x} obtained by the crystallization from a melt with excess of iron less than 1 mol%. The samples from a melt contain up to 78% of tetragonal phase, as estimated by the X-ray diffraction. Lattice parameters and unit cell volume for the samples exhibiting highest T_{c} and sharpest transition to superconducting state are limited to narrow range, with c/a ratio close to 1.469. The samples with excess of selenium contain higher amount of hexagonal phase than stoichiometric one. Superconducting single-crystalline samples of FeTe_{1 - y}Se_{y} (up to 100% of tetragonal phase) were obtained using Bridgman's method. When y value increases, the volume of unit cell decreases. The critical temperature T_{c} changes from ≈ 11.5 K for y ≈ 0.3 to ≈ 14.7 K for y ≈ 0.5.
11
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Geometrically Frustrated Kagome Lattice with Chemical Disorder

62%
Szymczak R., Baran M., Fink-Finowicki J., Krzymanska B., Aleshkevych P., Szymczak H.
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EN
The effect of nonmagnetic Mg^{2+} and magnetic Co^{2+} doping in Kagome compounds was investigated using DC magnetic susceptibility. The main effect of doping is to change the crystal field parameters. It was shown that Co^{2+} doping increases considerably crystal field parameters in Ni_3V_2O_8 while doping with nonmagnetic Mg^{2+} ions decreases considerably crystal field parameters in Co_3V_2O_8 crystals.
12
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Electrical Transport and Magnetic Properties of La_{2/3}Pb_{1/3}MnO_3 Thin Films

52%
Baran M., Berkowski M., Fink-Finowicki J., Lewandowski S., Szymczak H., Szymczak R., Khartchev S., Medvedev Y.
Acta Physica Polonica A
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2004
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vol. 105
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issue 1-2
115-120
EN
The magnetic and transport properties of epitaxial La_{2/3}Pb_{1/3}CuO_3 thin films deposited on SrLaGaO_4 substrate using dc magnetron sputtering technique are reported. The giant magnetoresistance effect (of about 50% at magnetic field of 1 T) was observed near the Curie temperature. Several mechanisms responsible for temperature dependence of resistivity are discussed. The effect of annealing was studied. It shifted the Curie temperature to the lower value, probably, because of the loss of oxygen.
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