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Wyświetlanie 1-10 z 10
Tytuł:
Semiconductor Superlattices with Small Band Offsets - feature article
Autorzy:
Yang, G.
Lewandowski, L. A.
Furdyna, J. K.
Ram-Mohan, L. R.
Powiązania:
https://bibliotekanauki.pl/articles/1968871.pdf
Data publikacji:
1998-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.66.-w
Opis:
Optical transitions in small band offset superlattices are studied within the framework of the nearly free electron approximation, in which the weak superlattice potential is treated as a perturbation. Interband selection rules are derived for transitions involving conduction and valence band states at the superlattice Brillouin zone center and the zone edge. It is found that a number of new transitions can occur in such small-offset superlattices due to wave function mixing of different subband states. The effect of the effective mass on the optical transitions is also discussed. The theory is used to explain the results observed in magneto-optical absorption experiment in ZnSe/Zn$\text{}_{1-x}$Mn$\text{}_{x}$Se small-offset superlattices. Furthermore, the nearly free electron formulation is found to be in excellent agreement with rigorous multi-band numerical calculation on superlattices involving small band offsets.
Źródło:
Acta Physica Polonica A; 1998, 93, 4; 567-600
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Diblock Copolymer Melt in Spherical Unit Cells of Higher Dimensionalities
Autorzy:
Banaszak, M.
Koper, A.
Knychała, P.
Lewandowski, K.
Powiązania:
https://bibliotekanauki.pl/articles/1489939.pdf
Data publikacji:
2012-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.35.Jk
Opis:
Using self-consistent field theory in spherical unit cells of various dimensionality, D = 1, 2, 3, and 4, we calculate phase diagram of a diblock, A-b-B, copolymer melt in 4-dimensional space, d = 4. The phase diagram is parameterized by the chain composition, f, and incompatibility between A and B, quantified by the product χ N. We predict 4 stable nanophases: layers, cylinders, 3D spherical cells, and 4D spherical cells. We also calculate order-disorder and order-order transition lines. In the strong segregation limit, that is for large χ N, the order-order transition compositions are determined by the strong segregation theory in its simplest form, for D = 1, 2, 3, and 4.
Źródło:
Acta Physica Polonica A; 2012, 121, 3; 703-710
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oxidation Kinetics of Thin and Ultrathin Fe Films
Autorzy:
Marczyńska, A.
Skoryna, J.
Lewandowski, M.
Smardz, L.
Powiązania:
https://bibliotekanauki.pl/articles/1387032.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.70.-i
68.55.-a
Opis:
We have studied oxidation kinetics of Fe thin films under atmospheric conditions using the fact that metallic iron is a ferromagnet but ultrathin natural iron oxides are practically nonmagnetic at room temperature. As a consequence, oxidation is associated with a loss in ferromagnetism. Fe thin films were deposited onto 1.5 nm V thick buffer layer using UHV magnetron sputtering. As a substrate we have used Si(100) wafers with an oxidised surface. Results show that all samples with an initial Fe thickness greater than 6 nm oxidize practically instantaneously, whereby a constant amount of 2.5 nm of metal is transformed into oxides. For iron thickness lower than 6 nm the time constant for oxidation increases considerably reaching a value of 30 days for the initial Fe thickness equal to 4 nm.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 549-551
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Atomic Order and the Interaction of Electronic and Magnetic Subsystems in Epitaxial LaSr(Ca)MnO Films
Autorzy:
Okunev, V. D.
Samoilenko, Z. A.
D'yachenko, T.
Abal'oshev, A.
Baran, M.
Gierłowski, P.
Lewandowski, S. J.
Szewczyk, A.
Szymczak, R.
Powiązania:
https://bibliotekanauki.pl/articles/2037110.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Kz
75.47.Lx
61.50.Ks
Opis:
We have investigated the structure, and electric, optical, and magnetic properties of LaSr(Ca)MnO films containing atomic clusters of various types coherently built into the basic crystallographic matrix. Below the transition to the metallic state, the electrical conductivity of the films is determined by tunneling of charge carriers between metallic clusters. We have found that for each sample there exists a threshold value of magnetic ordering, above which the magnetic subsystem starts to affect actively the film conductivity. The observed increase of conductivity with decreasing temperature is caused by the fact that in the process of magnetic ordering of the samples the cluster size and concentration of metallic phase increase. Experimental results are in agreement with theoretical calculations.
Źródło:
Acta Physica Polonica A; 2004, 105, 1-2; 121-126
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Application of Ultrasonic Methods to Flow Measurement and Detection of Microembolus in Heart Prostheses
Autorzy:
Gawlikowski, M.
Lewandowski, M.
Nowicki, A.
Kustosz, R.
Walczak, M.
Karwat, P.
Karłowicz, P.
Powiązania:
https://bibliotekanauki.pl/articles/1399342.pdf
Data publikacji:
2013-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.35.Yb
43.80.Qf
43.35.Ae
Opis:
For the last 20 years the world cardiosurgery has presented a considerable change of attitude to mechanical circulatory support. In spite of technological progress the main problems in ventricular assist devices are: thrombosis and low accuracy of flow measurements. In this paper the prototype of multi-gate Doppler flowmeter intended for cardiac assist system ReligaHeart EXT has been presented as well as the possibility of ultrasonic microembolus detection.
Źródło:
Acta Physica Polonica A; 2013, 124, 3; 417-420
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mesoscopic Ordering Effects in Single-Crystalline Thin Films of Lanthanum Manganites
Autorzy:
Samoilenko, Z. A.
Okunev, V. D.
Pushenko, E. I.
Abal'oshev, A.
Baran, M.
Gierłowski, P.
Lewandowski, S. J.
Szymczak, R.
Powiązania:
https://bibliotekanauki.pl/articles/2037100.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Kz
75.47.Lx
61.50.Ks
Opis:
We have investigated thin films of lanthanum manganites epitaxially grown by pulsed laser deposition on single-crystalline substrates. X-ray diffraction studies show that the characteristic feature of the investigated films is a superposition of fractions with long range atomic order in the basic single-crystalline matrix, and mesoscopic order in the clusterized structure encompassing the Mn-O layers. A detailed analysis of diffusive scattering shows that the size of metallic clusters and their volume concentration in the dielectric matrix varies. In the case of a small size and concentration, the metallic clusters in low temperature behave as quantum dots and their presence leads to a tunneling mechanism of conductivity with characteristic R(T)= const. In the case of large cluster size, the discrete energy levels become smeared. It appears also that the optical, transport, and magnetic properties of the investigated films depend critically on the distribution of Mn$\text{}^{2+}$, Mn$\text{}^{3+}$, and Mn$\text{}^{4+}$ ions in the clusters.
Źródło:
Acta Physica Polonica A; 2004, 105, 1-2; 93-98
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of FeSeTe Compound Crystallized from Liquid Phase
Autorzy:
Lewandowski, S.
Berkowski, M.
Tarenkov, V.
D'yachenko, A.
Abal'oshev, A.
Abal'osheva, I.
Gawryluk, D.
Domukhovski, V.
Sidorov, S.
Boichenko, D.
Powiązania:
https://bibliotekanauki.pl/articles/1536749.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Ha
74.45.+c
74.62.Bf
74.70.Xa
75.30.Cr
Opis:
We report on measurements of samples with nominal composition $FeSe_{0.5}Te_{0.5}$, crystallized by the Bridgman method. Magnetic and transport properties of the samples were examined. The measurements confirm the coexistence of ferromagnetism and superconductivity below the superconducting transition temperature. The ferromagnetic contribution to magnetization, estimated at 10%, might be caused by the presence of ferrimagnetic $Fe_7Se_8$, which occupies about 10% of sample volume. From the Andreev spectroscopy we found superconducting energy gap Δ = 2.6 meV at T = 4.2 K, and from magnetization measurements the critical temperature $T_c$ = 15.8 K. The critical current density in magnetic field H = 4 kOe, determined from magnetization measurements, is $j_c$ = (1-2) × 1$0^4$ A/$cm^2$ and weakly depends on magnetic field intensity.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 289-291
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tunneling Conductivity of Manganites with Negative Magnetoresistance
Autorzy:
Medvedev, Yu. V.
Tarenkov, V. Yu.
Svistunov, V. M.
Abaloshev, A. V.
Abalosheva, I. S.
Lewandowski, S. J.
Powiązania:
https://bibliotekanauki.pl/articles/2013683.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.70.Pa
Opis:
Tunneling investigations of ferromagnetic La$\text{}_{0.6}$Sr$\text{}_{0.4}$MnO$\text{}_{3}$ ceramic samples showing negative magnetoresistance effect were carried out in two types of junctions: symmetric "break junctions" and asymmetric ceramics-insulator-metal junctions. The results are consistent with the presence of small ferromagnetic clusters in the insulating barriers of both types of junctions and suggest a two-phase state realized by impurity mechanism of phase separation.
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 827-830
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of Excimer Laser Irradiation Effects on Properties of Crystalline YBaCuO Thin Films
Autorzy:
Abal'oshev, A.
Abal'osheva, I.
Lewandowski, S. J.
van der Beek, C. J.
Konczykowski, M.
Rizza, G.
Barbanera, S.
Powiązania:
https://bibliotekanauki.pl/articles/2038396.pdf
Data publikacji:
2004-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Fy
74.72.Bk
74.78.Bz
81.15.Fg
Opis:
The influence of UV laser irradiation on the physical properties of epitaxial YBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-δ}$ thin (<1μm) films fabricated by laser ablation was studied. The samples were irradiated by pulsed excimer laser beam at different incident energy densities E$\text{}_{ir}$≤130 mJ/cm$\text{}^{2}$, i.e. 2-3 times below the ablation threshold of YBaCuO. The analysis of the sample cross-section using transmission electron microscope shows that such irradiation forms a disordered layer on the top of the crystalline film. Sample surface amorphization was observed also by atomic force microscope. Due to strong UV irradiation absorption in YBaCuO this surface layer acts like a protective cover for the sample interior. Only a small reduction of superconducting critical temperature T$\text{}_{c}$ was observed. Both transport measurements in normal state and magneto-optical studies in superconducting state indicate that between the disordered layer and the bottom non-modified part of the film there exists a wide transitional region with reduced carrier concentration.
Źródło:
Acta Physica Polonica A; 2004, 106, 5; 681-685
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of Bragg and Polarimetric Optical Fiber Sensors for Stress Monitoring in Composite Materials
Autorzy:
Domanski, A.
Lesiak, P.
Milenko, K.
Budaszewski, D.
Chychlowski, M.
Ertman, S.
Tefelska, M.
Wolinski, T.
Jedrzejewski, K.
Lewandowski, L.
Jasiewicz, W.
Helsztynski, J.
Boczkowska, A.
Powiązania:
https://bibliotekanauki.pl/articles/1795792.pdf
Data publikacji:
2009-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.81.Gs
42.81.Pa
62.23.Pq
Opis:
Composite structures are made of two or more components with significantly different physical or chemical properties and they remain separate and distinct in a macroscopic level within the finished structure. This feature allows for introducing optical fiber sensors into the composite material. These sensors can demonstrate stress distribution inside tested material influenced by external tensions. Two types of the optical fiber sensors are used as the 3D structure. One of them is based on application of fiber Bragg grating inside the core of the fiber. Longitudinal stress changes parameters of the Bragg grating and simultaneously, spectral characteristics of the light transmitted through the fiber. The second one is based on application of highly birefringent fibers which, under external stress, introduce polarization changes of the output light.
Źródło:
Acta Physica Polonica A; 2009, 116, 3; 294-297
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-10 z 10

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