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Wyświetlanie 1-11 z 11
Tytuł:
The Pressure Effects on Electronic Structure of Iron Chalcogenide Superconductors $FeSe_{1-x}Te_x$
Autorzy:
Ciechan, A.
Winiarski, M.
Samsel-Czekała, M.
Powiązania:
https://bibliotekanauki.pl/articles/1431323.pdf
Data publikacji:
2012-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Pq
74.25.Kc
74.62.F
74.70.Xa
Opis:
We study the electronic structure of iron-based superconductors $FeSe_{1-x}Te_x$ within the density functional theory. We pay particular attention to the pressure effects on the Fermi surface (FS) topology, which seem to be correlated with a critical superconducting temperature $T_C$ of iron chalcogenides and pnictides. A reduction of the FS nesting between hole and electron cylinders with increasing pressure is observed, which can lead to higher values of $T_C$. The tellurium substitution into selenium sites yields FS changes similar to the pressure effect.
Źródło:
Acta Physica Polonica A; 2012, 121, 4; 820-823
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetoresistance of Si/Nb/Si Trilayers
Autorzy:
Zaytseva, I.
Cieplak, M.
Abal'oshev, A.
Dluzewski, P.
Grabecki, G.
Plesiewicz, W.
Zhu, L.
Chien, C.
Powiązania:
https://bibliotekanauki.pl/articles/1537220.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.62.-c
74.25.F-
74.25.Ha
74.62.En
Opis:
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.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 406-408
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Impact of Strain on the Superconducting Properties of Strongly Underdoped $La_{2-x}Sr_xCuO_4$ Thin Films
Autorzy:
Zaytseva, I.
Cieplak, M.
Paszkowicz, W.
Abal'oshev, A.
Berkowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1431516.pdf
Data publikacji:
2012-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.F-
74.62.En
74.78.-w
Opis:
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.
Źródło:
Acta Physica Polonica A; 2012, 121, 4; 858-865
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Iron Substitutions on the Transport Properties of $FeTe_{0.65}Se_{0.35}$ Single Crystals
Autorzy:
Bezusyy, V.
Gawryluk, D.
Malinowski, A.
Berkowski, M.
Cieplak, M.
Powiązania:
https://bibliotekanauki.pl/articles/1374765.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.F-
74.62.Dh
74.70.Xa
Opis:
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.
Źródło:
Acta Physica Polonica A; 2014, 126, 4a; A-76-A-79
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Pressure on Superconductivity in $YB_{6}$
Autorzy:
Gabáni, S.
Pristáš, G.
Takáčová, I.
Flachbart, K.
Gažo, E.
Mori, T.
Braithwaite, D.
Samuely, P.
Powiązania:
https://bibliotekanauki.pl/articles/1371520.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.70.Ad
74.25.F-
62.50.-p
Opis:
Magnetoresistivity measurements on a superconducting system of $YB_{6}$ ($T_c$ ≈7.5 K) down to 60 mK at hydrostatic pressures up to 47 kbar are presented. The superconducting transition temperature, as well as the third critical field $H_{c3}$ reveal a linear decrease with increasing pressure with slopes of d ln $H_{c3}$/dp=-1.1 %/kbar, and d ln $T_c$/dp=-0.59 %/kbar. From the latter a critical pressure, $p_c$ ≈ 170 kbar, at which $T_c$ vanishes, is determined.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 340-341
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Doping Effects of Co, Ni, and Cu in $FeTe_{0.65}Se_{0.35}$ Single Crystals
Autorzy:
Bezusyy, V.
Gawryluk, D.
Berkowski, M.
Cieplak, M.
Powiązania:
https://bibliotekanauki.pl/articles/1431291.pdf
Data publikacji:
2012-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.F-
74.25.Op
74.62.Dh
74.70.Xa
Opis:
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.
Źródło:
Acta Physica Polonica A; 2012, 121, 4; 816-819
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fabrication and Transport Critical Current Densities of $MgB_2//Fe//Cu$ Multifilament Tapes without Any Intermediate Annealing
Autorzy:
Yucel, E.
Terzioglu, C.
Varilci, A.
Gencer, A.
Belenli, I.
Powiązania:
https://bibliotekanauki.pl/articles/1489874.pdf
Data publikacji:
2012-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.70.Ad
84.71.Mn
74.62.-c
74.25.Sv
74.25.F-
Opis:
We have fabricated superconducting 6 and 7 filaments $MgB_2//Fe//Cu$ tapes by ex situ powder-in-tube method using Cu-sheath without any intermediate annealing. Properties of two different multicore $MgB_2//Fe//Cu$ tapes annealed at 900C for 2 h in high purity argon gas atmosphere were compared. The samples were characterized using scanning electron microscope, X-ray diffraction, electron dispersive spectroscopy, optical microscopy, critical transition temperature, transport critical current density, and magnetic measurements. Transport critical current densities of the 6 and 7 filaments tapes were found to be 450 A/cm^2 and 190 A/cm^2 at 20 K, respectively. From X-ray diffraction measurements, lattice parameters a and c were determined. From dc resistivity measurements, the connectivity between grains was investigated by using Rowell's connectivity analysis.
Źródło:
Acta Physica Polonica A; 2012, 121, 3; 660-665
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Pressure on the Electron-Phonon Interaction in Superconductors
Autorzy:
Orendáč, Mat.
Gabáni, S.
Pristáš, G.
Gažo, E.
Shitsevalova, N.
Flachbart, K.
Powiązania:
https://bibliotekanauki.pl/articles/1030277.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.70.Ad
72.15.Eb
74.62.Fj
74.25.F-
63.20.kd
Opis:
The electron-phonon interaction is a very important and ubiquitous process in solids, affecting almost all their physical properties. In metals, where the relaxation processes depend on both electrons and phonons, all thermodynamic and transport properties are dictated by the electron-phonon interaction. A very strong manifestation of the electron-phonon interaction is related with the superconducting state. Here we report the effect of high pressure on the transport electron-phonon interaction, λ_{tr}, in superconducting systems such as YB_6 (T_c ≈ 7.5 K), Pb (T_c ≈7.2 K), Nb bulk or thin film (T_c ≈9.2 K), and in LaB_6 in which superconductivity was not yet observed. The expected pressure effect should correspond to the theoretically predicted negative pressure effect on T_c (except for Nb thin film and LaB_6). To determine the influence of pressure on λ_{tr}, we utilized the Bloch-Grüneisen fit (denoted also as "thermal spectroscopy") of the precise temperature dependence of resistivity measurements in the normal state up to a pressure of 2.8 GPa. Based on this fit the observed negative pressure effect on λ_{tr} values, dλ_{tr}/dp, are as follows: dλ_{tr}/dp ≈-0.045 GPa^{-1} for YB_6, dλ_{tr}/dp ≈-0.13 GPa^{-1} for Pb, dλ_{tr}/dp ≈-0.019 GPa^{-1} or -0.028 GPa^{-1} for Nb bulk or thin film, respectively, and dλ_{tr}/dp ≈-0.003 GPa^{-1} for LaB_6.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 1039-1041
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Superconducting and Magnetic States in $RuSr_2GdCu_2O_8$, Based on the Magnetic, Transport and Magneto-Caloric Characteristics
Autorzy:
Klamut, P.
Plackowski, T.
Powiązania:
https://bibliotekanauki.pl/articles/1536600.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.72.-h
75.30.-m
74.62.Bf
74.25.F-
75.30.Sg
Opis:
The article discusses selected properties of the non- and superconducting polycrystalline samples of $RuSr_2GdCu_2O_8$ and comments on the consequences of introducing insignificant sub-stoichiometry of Ru into the nominal formula. The magneto-resistive and the magnetic characteristics are interpreted in favour of the formation of intrinsically inhomogeneous superconducting phase, which seems stabilized along with the structural modifications enhanced with the modification of starting stoichiometry. The specific heat data reveals the small shift of the temperature of magnetic ordering $T_{m}$, which may suggest dilution of the magnetic sublattice of the Ru moments. The measurements of the magnetic field dependences of the isothermal magnetocaloric coefficient $M_{T}$ reveal no gain in the system magnetic entropy in a broad range of accessed fields and temperature. Whereas the multi-component character of the compound's magnetsm precludes from concluding on the magnetic ground state, the maximum in $M_T (H)$, which occurs at comparably weak magnetic field for temperatures in a vicinity of $T_{m}$ may reflect dominance of the ferromagnetic type interactions with a constrained correlation range. The literature explored models for the Ru magnetic ordering and also possible phase separation are brought into the discussion.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 254-260
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Phase Diagram of $TmB_{4}$ under High Pressure
Autorzy:
Gabáni, S.
Pristáš, G.
Takáčová, I.
Flachbart, K.
Filipov, V.
Shitsevalova, N.
Siemensmeyer, K.
Powiązania:
https://bibliotekanauki.pl/articles/1371562.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Kz
75.25.+z
74.25.F
62.50.-p
Opis:
$TmB_{4}$ is a Shastry-Sutherland frustrated system which exhibits very complex magnetic properties. In this contribution the phase diagram of magnetic field vs. temperature of $TmB_{4}$ under hydrostatic pressure up to 26.5 kbar is investigated using sensitive ac-resistance measurements. Temperature and magnetic field dependences of resistance at various pressures were carried out in a piston cylinder pressure cell between 1.7 and 14 K and in magnetic fields up to 6 T. The obtained results exhibit shifts of ordering temperatures $T_{N}$ as well as shifts of boundaries between different magnetic phases. The observed pressure dependences of $T_{N}$ can be described by the relation d $lnT_{N}$/dp=+(0.16÷0.18) %/kbar. The effect of pressure on various interactions between magnetic ions in this compound is discussed.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 356-357
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Diagram and Activation Energy for Vortex Pinning in Nb/(Co,Pd) Superconductor-Ferromagnet Bilayer
Autorzy:
Syryanyy, Y.
Aleszkiewicz, M.
Cieplak, Marta
Zhu, L.
Chien, C.
Powiązania:
https://bibliotekanauki.pl/articles/1374109.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.F-
74.25.N-
74.25.Wx
74.62.-c
74.70.-b
74.78.-w
74.78.Fk
75.70.Kw
75.70.-i
Opis:
Using the magnetoresistance measurements we study the phase transition line and the activation energy for vortex pinning in superconductor/ferromagnet bilayer, built of a ferromagnetic Co/Pd multilayer with perpendicular magnetic anisotropy, and a niobium film, with insulating layer in-between to eliminate proximity effect. The domain width is reversibly pre-defined using the angle-dependent demagnetization. We find that the enhancement of the activation energy for vortex pinning by magnetic domains is rather modest, by a factor of about 2.1. We attribute this to large domain width, and large dispersion of the domain width in this bilayer.
Źródło:
Acta Physica Polonica A; 2014, 126, 4a; A-123-A-126
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-11 z 11

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