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1
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Tests of the Structure-Based Models of Proteins

100%
Cieplak M., Sułkowska J.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
441-445
EN
The structure-based models of proteins are defined through the condition that their ground state coincides with the native structure of the proteins. There are many variants of such models and they yield different properties. Optimal variants can be selected by making comparisons to experimental data on single-molecule stretching. Here, we discuss the 15 best performing variants and focus on fine tuning the selection process by adjusting the velocity of stretching to match the experimental conditions. The very best variant is found to correspond to the 10-12 potential in the native contacts with the energies modulated by the Miyazawa-Jernigan statistical potential and variable length parameters. The second best model incorporates the Lennard-Jones potential with uniform amplitudes. We then make a detailed comparison of the two models in which theoretical surveys of stretching properties of 7510 proteins were made previously.
2
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Enhancement of Flux Pinning in the Superconductor-Ferromagnet Bilayer Nb(Co/Pd)

81%
Syryanyy Y., Zhu L., Cieplak M., Chien C.
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issue 2
399-401
EN
The magnetometry and the magnetic force microscopy are used to study the influence of the magnetic domain size on the flux pinning in a superconducting/ferromagnetic bilayer (SFB), in which the S layer is niobium and the F layer is a Co/Pd multilayer with perpendicular magnetic anisotropy. The domain size is pre-defined using the angle-dependent demagnetization. The enhancement of pinning is found to be the strongest, up to a factor of 6, for narrow domains and small magnetic fields. This result differs from the behavior observed in the SFB in which the F layer is Co/Pt. The difference may be attributed to the degree of the disorder in the domain pattern.
3
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Doping Effects of Co, Ni, and Cu in FeTe_{0.65}Se_{0.35} Single Crystals

81%
Bezusyy V., Gawryluk D., Berkowski M., Cieplak M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
816-819
EN
The resistivity, magnetoresistance, and magnetic susceptibility are measured in single crystals of FeTe_{0.65}Se_{0.35} with Cu, Ni, and Co substitutions for Fe. The crystals are grown by Bridgman's method. The resistivity measurements show that superconductivity disappears with the rate which correlates with the nominal valence of the impurity. From magnetoresistance we evaluate doping effect on the basic superconducting parameters, such as upper critical field and coherence length. We find indications that doping leads to two component superconducting behavior, possibly because of local charge depression around impurities.
4
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Negative Magnetoresistance in the Variable-Range-Hopping Transport of Strongly Underdoped La_{2-x}Sr_xCuO_4

81%
Malinowski A., Cieplak M., Berkowski M., Guha S.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
611-615
EN
The in-plane transport of strongly underdoped La_{2-x}Sr_xCuO_4 films was examined in the magnetic fields up to 14 T and in temperatures down to 1.6 K. While at high temperatures the samples display metallic-like resistivity, the low-T transport is governed by variable-range-hopping mechanism. Careful analysis shows that the temperature dependence of pre-exponential factor in Mott's variable-range-hopping law may not be neglected and that the density of states at the Fermi level can be effectively expressed as g(E-E_F)=N_0 (E-E_F)^p, with a small exponent p of the order of 0.1. In the magnetic field parallel to CuO_2 planes one of the variable-range-hopping parameter,ρ_0, increases by about 20-25%, while the other one, T_0, decreases by about 10-15%, resulting in the decrease in total resistivity. This effect may be related to the decrease of the tunneling barrier between different antiferromagnetic clusters in the presence of magnetic field.
5
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Impact of Strain on the Superconducting Properties of Strongly Underdoped La_{2-x}Sr_xCuO_4 Thin Films

71%
Zaytseva I., Cieplak M., Paszkowicz W., Abal'oshev A., Berkowski M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
858-865
EN
Using pulsed laser deposition we have grown films of La_{2-x}Sr_xCuO_4 with x in close vicinity of the superconductor-insulator transition, x=0.051 and x=0.048, on SrLaAlO_4 substrates, and of different thickness d (from 25 nm to 250 nm). The X-ray diffraction shows that for each d the films grow with variable degree of compressive in-plane strain, with the largest strain achieved in thinnest films. The resistivity measurements show strong enhancement of superconductivity with increasing strain, so that the onset of superconductivity at temperature as high as 27 K is observed. With increasing strain the character of resistivity changes from the insulating to metallic.
6
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Inhomogeneous Magnetic Field Penetration in Superconducting Niobium Films

71%
Abal'osheva I., Abal'oshev A., Cieplak M., Zhu L., Chien C.
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issue 2
396-398
EN
The peculiarities of magnetic field penetration in the form of fingering or dendritic instabilities are studied by magneto-optical technique in the niobium films of different thickness. It is observed that the reduction of Nb film thickness reduces the threshold field for instabilities, in agreement with the theoretical predictions. In addition, it is shown that the silver overlayer deposited on the top of Nb film leads also to the enhancement of instabilities, in marked contrast to the effect of gold or aluminum overlayers, which are known to suppress instabilities.
7
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Vortex Dynamics in Ferromagnetic/Superconducting Bilayers

71%
Cieplak M., Adamus Z., Kończykowski M., Zhu L., Chien C.
Acta Physica Polonica A
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2008
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vol. 114
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issue 1
23-28
EN
The dependence of vortex dynamics on the geometry of magnetic domain pattern is studied in the superconducting/ferromagnetic bilayers, in which niobium is a superconductor, and Co/Pt multilayer with perpendicular magnetic anisotropy serves as a ferrromagnetic layer. Magnetic domain patterns with different density of domains per surface area and different domain size, w, are obtained for Co/Pt with different thickness of Pt. The dense patterns of domains with the size comparable to the magnetic penetration depth (w≥λ) produce large vortex pinning and smooth vortex penetration, while less dense patterns with larger domains (w ≫ λ) enhance pinning less effectively and result in flux jumps during flux motion.
8
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Influence of Iron Substitutions on the Transport Properties of FeTe_{0.65}Se_{0.35} Single Crystals

71%
Bezusyy V., Gawryluk D., Malinowski A., Berkowski M., Cieplak M.
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vol. 126
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issue 4a
A-76-A-80
EN
We study the ab-plane resistivity and Hall effect in the single crystals of Fe_{1-y}M_yTe_{0.65}Se_{0.35}, where M = Co or Ni (0 ≤ y ≤ 0.21). In case of each dopant two types of crystals, with different crystalline quality, are prepared by Bridgman's method using different cooling rates, fast or slow. The impurities suppress the superconducting transition temperature, T_c, with different rates. T_c reaches zero at markedly different impurity content: only 3 at.% of Ni, and about 14 at.% of Co. In addition, the suppression is somewhat dependent on the crystal cooling rate. The resistivity at the onset of superconductivity rises only weakly with the Co doping, while it increases 10 times faster for Ni. The Hall coefficient R_{H} is positive for Co doping indicating that hole carriers dominate the transport. For Ni R_{H} changes sign into negative at low temperatures for crystals with the Ni content exceeding 6 at.%. The implications of these results are discussed.
9
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Metal-Insulator Transition in Zinc-Doped LaSrCuO

71%
Malinowski A., Cieplak M., Berkowski M., Plesiewicz W., Skośkiewicz T.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
617-621
EN
The magnetotransport in the vicinity of the metal-insulator transition in La_{1.85}Sr_{0.15}Cu_xZn_{1-x}O_4 is studied in the mK temperature range. Both longitudinal and transverse magnetoresistance are negative indicating the importance of spin effects. The magnitude of transverse magnetoresistance is larger than the magnitude of longitudinal magnetoresistance, indicating the absence of positive orbital magnetoresistance, in sharp contrast to strongly underdoped La_{2-x}Sr_xCuO_4. Both transverse and longitudinal magnetoresistance are proportional to the relative change of zero-field conductivity. This suggests that low-temperature localization of carriers may originate in the spin-disorder scattering on the spin droplets around Zn-impurities.
10
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Strain Relaxation in Thin Films of La_{1.85}Sr_{0.15}CuO_4 Grown by Pulsed Laser Deposition

62%
Zaytseva I., Cieplak M., Abal'oshev A., Berkowski M., Domukhovski V., Paszkowicz W., Shalimov A.
Acta Physica Polonica A
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2007
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vol. 111
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issue 1
185-188
EN
X-ray diffraction, resistivity, and susceptibility measurements are used to examine the effects of film thickness d (from 17 to 250 nm) on the structural and superconducting properties of La_{1.85}Sr_{0.15}CuO_4 films grown by pulsed laser deposition on SrLaAlO_4 substrates. For each d the film sgrow with a variable strain, ranging from a large compressive strain in the thinnest films to a negligible or tensile strain in thick films. Our results indicate that the tensile strain is not caused by the off-stoichiometric layer at the substrate-film interface. Instead, it may be caused by the extreme oxygen deficiency in some of the films.
11
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Effect of the In-Plane Epitaxial Mismatch between the Substrate and the Film on the Properties of YBa_2Cu_3O_{7-δ} Films

62%
Abal'osheva I., Cieplak M., Adamus Z., Berkowski M., Domukhovski V., Aleszkiewicz M.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
549-554
EN
We study the effect of the in-plane epitaxial mismatch between the substrate and the film on the crystallographic structure and the transport properties of YBa_2Cu_3O_{7-δ} superconducting films of thicknesses ranging between 600 and 3000Å. The films are grown by pulsed laser deposition on the new type of single-crystalline substrates prepared by Czochralski method, with the chemical formula (SrAl_{0.5}Ta_{0.5}O_3)_{0.7}(CaAl_{0.5}Ta_{0.5}O_3)_{0 .1}(LaAlO_3)_{0.2}. We find that superconducting properties of the samples are excellent, and generally they improve with increasing of the film thickness as a result of improved structural ordering. We also investigate the influence of the film thickness on the behavior of the critical current densities.
12
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Flux Penetration in a Ferromagnetic/Superconducting Bilayer

62%
Adamus Z., Cieplak M., Abal'oshev A., Kończykowski M., Cheng X., Zhu L., Chien C.
Acta Physica Polonica A
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2007
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vol. 111
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issue 1
95-98
EN
An array of miniature Hall sensors is used to study the magnetic flux penetration in a ferromagnetic/superconducting bilayer consisting of Nb as a superconducting layer and Co/Pt multilayer with perpendicular magnetic anisotropy as a ferromagnetic layer, separated by an amorphous Si layer to avoid the proximity effect. It is found that the magnetic domains in the ferromagnetic layer create a large edge barrier in the superconducting layer which delays flux penetration. The smooth flux profiles observed in the absence of magnetic pinning change into terraced profiles in the presence of domains.
13
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Microstructure of the Pulsed Laser Deposited LaSrCuO Films

62%
Cieplak M., Abal'oshev A., Zaytseva I., Berkowski M., Guha S., Wu Q.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
573-576
EN
The X-ray diffraction and atomic force microscopy are used to examine the microstructure of La_{1.85}Sr_{0.15}CuO_4 films grown by pulsed laser deposition on LaSrAlO_4 substrates. The films grow with different degrees of built-in strain, ranging from a large compressive to a large tensile in-plain strain. The tensile strain cannot be attributed to a substrate-related strain. The possible origins of the tensile strain are discussed.
14
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Magnetoresistance of Si/Nb/Si Trilayers

52%
Zaytseva I., Cieplak M., Abal'oshev A., Dluzewski P., Grabecki G., Plesiewicz W., Zhu L., Chien C.
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issue 2
406-408
EN
We study the superconductor-insulator transition in Si/Nb/Si trilayers, in which the thickness of Si is fixed at 10 nm, and the nominal thickness of Nb changes in the range between d = 20 nm down to d = 0.3 nm. The transmission electron microscopy indicates the formation of the mixed Nb-Si layer for small d. Both the thickness-induced, and the magnetic-field induced superconductor-insulator transition is observed. The crossing point of the isotherms at the critical field B_{c} decreases with decreasing d, and it is T-independent at temperatures below 300 mK. At larger fields the weak peak in magnetoresistance appears in some of the films.
15
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Vortex Pinning in Ferromagnet/Superconductor Bilayers - the Dependence on the Ferromagnetic Layer and Temperature

52%
Adamus Z., Cieplak M., Abal'oshev A., Berkowski M., Kończykowski M., Cheng X., Shu L., Chien C.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
451-456
EN
The behavior of vortex pinning induced by the magnetic domain reversal is studied in the ferromagnet/superconductor bilayers in which superconducting film is niobium and the ferromagnetic layers are the Co/Pt superlattices with perpendicular magnetic anisotropy. The local magnetic field across narrow ferromagnet/superconductor bilayer stripe is measured using a line of miniature Hall sensors. The pinning is studied for samples with different amount of repeats of Co/Pt superlattice, and as a function of temperature.
16
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Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer

52%
Cieplak M., Adamus Z., Konczykowski M., Chen X., Byczuk A., Abal'oshev A., Sang H., Chien C.
Acta Physica Polonica A
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2004
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vol. 106
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issue 5
693-698
EN
The local flux profile and the critical current are studied using an array of Hall sensors in a ferromagnetic-superconducting bilayer which consists of niobium film covering ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy. The results indicate about threefold enhancement of the flux pinning in niobium layer caused by the isolated magnetic domains which are created during the magnetization reversal of the Co/Pt multilayer. The geometrical barrier is absent, and the critical current is strongly peaked in close vicinity to the sample center, suggesting that the critical state differs from that predicted by the Bean model.
17
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Optimization of the Superconducting Properties of Laser Ablated YBa_2Cu_3O_{7-δ} Films on CeO_2-Buffered Sapphire

52%
Abal'osheva I., Zaytseva I., Aleszkiewicz M., Syryanyy Y., Gierłowski P., Abal'oshev O., Bezusyy V., Cieplak M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
805-807
EN
We use pulsed laser deposition to grow YBa_2Cu_3O_{7-δ} (YBCO) superconducting films for microwave applications. The films are grown on R-cut sapphire substrates, with CeO_2 buffer layers, which are re-crystallized at high temperature prior to YBCO growth. Using the atomic force microscopy (AFM) and X-ray diffractometry we determine the optimal temperature for recrystallization (1000°C) and the optimal buffer layer thickness (30 nm). The properties of YBCO films of various thickness, grown on the optimized CeO_2 buffer layers, are studied using several methods, including AFM, magnetooptical imaging, and transport experiments. The YBCO film roughness is found to increase with the increasing film thickness, but the magnetic flux penetration in the superconducting state remains homogeneous. The superconducting parameters (the critical temperature and the critical current density) are somewhat lower than the similar parameters for YBCO films deposited on mono-crystalline substrates.
18
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Growth and Characterization of YBa_2Cu_3O_{7-δ} Films Deposited by Laser Ablation on CeO_2-Buffered Sapphire

52%
Abal'osheva I., Zaytseva I., Aleszkiewicz M., Malinowski A., Bezusyy V., Syryanyy Y., Gierłowski P., Abal'oshev O., Kończykowski M., Cieplak M.
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vol. 126
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issue 4a
A-69-A-73
EN
In this work we study the growth, by pulsed laser deposition, of YBa_2Cu_3O_{7-δ} (YBCO) films on the CeO_2-buffered R-cut sapphire substrates, with the buffer layer recrystallized prior to the deposition of superconductor. We find that the superconducting critical temperature and the critical current density of the films are very close to similar parameters for the YBCO films grown on lattice-matched single crystalline substrates. It appears that the structural defects in the buffer layer affect the microstructure of YBCO films, resulting in high values of the critical current density, suitable for applications.
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