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1

Spontaneous Magnetostriction of Lu_2Fe_{17-x}Si_x

100%

Andreev A., Daniš S.

Acta Physica Polonica A

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2008

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vol. 113

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issue 1

239-242

EN

Thermal expansion of Lu_2 Fe_{17-x}Si_x solid solutions was measured by X-ray powder diffraction. The magnetic ordering in all compounds within the homogeneity range (x≤3. 4) is accompanied by a large spontaneous volume magnetostriction distributed anisotropically over the principal axes of the hexagonal crystal structure. The volume effect ω_s in the ground state reaches 14.7×10^{-3} in Lu_2Fe_{17} and decreases monotonously to 8.9×10^{-3} at x = 3.4 following the reduction of magnetic moment. Despite still large ω_s, the Invar behavior observed in Lu_2Fe_{17} changes to a positive thermal expansion for x >1 due to increasing Curie temperature.

2

Specific Heat and Magnetism of LuFe_6Al_6

81%

Svoboda P., Andreev A., Šantavá E., Šebek J.

Acta Physica Polonica A

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2008

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vol. 113

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issue 1

307-310

EN

Here we present the results of the zero-field specific heat study of the LuFe_6Al_6 single crystal. The specific heat data were analyzed as a sum of the phonon, electronic, and magnetic contributions, respectively. The analysis of the phonon part involves three acoustic and 36 optical branches, respectively, all of them corrected for the anharmonicity. The magnetic part of the specific heat was obtained by subtracting the electronic and the phonon part from the experimental specific heat and the magnetic entropy was calculated.

3

Magnetic Structure in UIrAl

81%

Prokeš K., Prchal J., Sechovský V., Andreev A.

Acta Physica Polonica A

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2008

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vol. 113

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issue 1

339-342

EN

By means of neutron diffraction on a hexagonal UIrAl single crystal we find that this system orders ferromagnetically at low temperatures with magnetic moments of 0.93 (10) μ_B aligned along the c axis. The Curie temperature T_C = 65 (5) K determined from the diffraction experiment is in good agreement with bulk magnetic measurements.

4

Magnetic Anisotropy of Lu_2Co_{17-x}Si_x Single Crystals

81%

Tereshina E., Andreev A., Šantavá E., Daniš S.

Acta Physica Polonica A

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2008

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vol. 113

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issue 1

235-238

EN

Magnetic anisotropy of Lu_2Co_{17-x}Si_x single crystals grown by the Czochralski method was investigated. The homogeneity range of Si substitution for Co extends up to x = 3.4 in Lu_2Co_{17-x}Si_x solid solutions. The unit cell volume, Curie temperature, and spontaneous magnetic moment decrease monotonously with increasing Si content. Lu_2Co_{17} has the easy-plane type of magnetic anisotropy in the ground state, which changes into the easy-axis type by two spin-reorientation transitions of the second-order, the easy-plane-easy-cone at T_{SR1}~680 K and the easy-cone - easy-axis at T_{SR2}~730 K. Upon Si substitution, the observed spin-reorientations shift towards the lower temperatures for Lu_2Co_{17-x}Si_x (T_{SR1}~75 K and T_{SR2}~130 K in Lu_2Co_{16}Si) and vanish for compounds with 1

5

Amorphous 5f Ferromagnetic Hydrides UH_{3}Mo_{x}

61%

Tkach I., Kim-Ngan N., Maškova S., Andreev A., Matěj Z., Havela L.

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EN

γ-U metal, stabilized down to room temperature in the bcc structure by Mo doping, can absorb hydrogen at high H_{2} pressures only. The product is amorphous hydride UH_{3}Mo_{x} analogous to β-UH_{3}. Such hydrides are ferromagnetic with high Curie temperatures (up to 200 K), enhanced with respect to β-UH_{3}. Magnetic moment of U also increases. Large disorder together with high anisotropy lead to a very high coercivity, reaching 4 T at low temperatures. As amorphization normally tends to suppress magnetic ordering of U compounds, such hydrides represent a new class of materials, amorphous U-based ferromagnets with relatively high Curie temperature.

6

Structure and Properties of Multilayer Nanostructured Coatings TiN/MoN Depending on Deposition Conditions

52%

Pogrebnjak A., Abadias G., Bondar O., Postolnyi B., Lisovenko M., Kyrychenko O., Andreev A., Beresnev V., Kolesnikov D., Opielak M.

Acta Physica Polonica A

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2014

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vol. 125

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issue 6

1280-1283

EN

This work presents the results of TiN/MoN coatings studying. These multilayer nanostructured coatings demonstrate dependence on depositions conditions on nanometer level. The influence of nanosized monolayer thickness on structure changing and properties of nanocomposite multilayer coatings TiN/MoN was found. Multilayer TiN/MoN coatings of the total thickness from 6.8 to 8.2 μm were obtained using C-PVD method. Thicknesses of monolayers were 2, 10, 20, 40 nm. The structure of samples was studied using X-ray diffraction (Bruker D-8 Advance) in Cu K_{α} radiation, high resolution transmission electron microscopy with diffraction CFEI EO Techai F200, scanning electron microscopy with energy dispersive X-ray spectroscopy (JEOL-7001F), and microhardness measurements in dependence on indenter load. Scratch tests (friction, wear, etc.) were also provided using Rockwell-C diamond indenter (CSM Revetest Instruments) with a tip radius of 200 μm. Friction and wear behavior were evaluated using ball-on-plate sliding test on a UMT-3MT tribometer (CETR, USA). With decreasing monolayer thickness the hardness value increases, and the size of nanograins reduces. The values obtained for the friction coefficient of the multilayer system is much smaller than in nanostructured coatings of TiN (nc) or MoN (nc). Annealing showed formation of a (Ti,Mo)N solid solution and small growth of nanocrystals.

7

Optically Active Si:Er Layers Grown by the Sublimation MBE Method

42%

Stepikhova M., Andreev A., Andreev B., Krasil'nik Z., Shmagin V., Kuznetsov V., Rubtsova R., Jantsch W., Ellmer H., Palmetshofer L., Preier H., Karpov Y., Piplits K., Hutter H.

Acta Physica Polonica A

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1998

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vol. 94

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issue 3

549-554

EN

We report the first application of sublimation molecular beam epitaxy to grow uniformly and selectively doped Si:Er layers with Er concentration up to 5×10^{18} cm^{-3}. The Hall concentration of electrons is about 10% of total Er contents. The mobility is 300-400 cm^{2} V^{-1} s^{-1} at 300 K. All samples exhibit photoluminescence at 1.537 μm up to 100-140 K.

8

Light Absorption and Photoluminescence in Quantum Dots and Artificial Molecules

37%

Firsov D., Vorobjev L., Panevin V., Fedosov N., Shalygin V., Samsonenko J., Tonkikh A., Cirlin G., Andreev A., Kryzhanovskaya N., Tarasov I., Pikhtin N., Ustinov V., Hanna S., Seilmeier A., Julien F., Zakharov N., Werner P.

Acta Physica Polonica A

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2005

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vol. 107

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issue 1

158-162

EN

Intraband absorption in n- and p-doped structures with InAs/GaAs quantum dots covered by InGaAs layers is studied both experimentally and theoretically. The absorption cross-section for p-type quantum dots was found to be significantly smaller than that for n-type quantum dots. Interband absorption bleaching under strong interband excitation is found and investigated in undoped quantum dot structures. Structures with artificial molecules were grown. Photoluminescence spectra and transmission electron microscopy images proves the presence of coupled symmetrical quantum dots.

Refine search results

Spontaneous Magnetostriction of Lu_2Fe_{17-x}Si_x

Specific Heat and Magnetism of LuFe_6Al_6

Magnetic Structure in UIrAl

Magnetic Anisotropy of Lu_2Co_{17-x}Si_x Single Crystals

Amorphous 5f Ferromagnetic Hydrides UH_{3}Mo_{x}

Structure and Properties of Multilayer Nanostructured Coatings TiN/MoN Depending on Deposition Conditions

Optically Active Si:Er Layers Grown by the Sublimation MBE Method

Light Absorption and Photoluminescence in Quantum Dots and Artificial Molecules