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Tytuł:
Magnetoresistance and Intrinsic Pinning of Vortices in the Untwinned $YBa_2Cu_3O_{7 - δ}$ Single Crystals with Optimal Oxygen Content and a Small Deviation from the Oxygen Stoichiometry
Autorzy:
Vovk, R.
Gvozdikov, V.
Obolenskii, M.
Nazyrov, Z.
Kruglyak, V.
Powiązania:
https://bibliotekanauki.pl/articles/1427580.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Fy
74.25.Qt
Opis:
We study the temperature dependence of the in-plane magnetoresistance $ρ_{ab}(T)$ in untwinned $YBa_2Cu_3O_{7 - δ}$ single crystals with the optimal oxygen content and with a small deficit of oxygen atoms at different angles between the external magnetic field 15 kOe and the ab-planes α. We found that at high temperatures in the pseudogap region external magnetic field does not affect the $ρ_{ab}(T)$ but it broadens transitional region $T_{c} - T_{c0}$ from 0.3 K at zero field and α = 0 to approximately 6 K at α = 60° in the field. In case of optimal doping the function $ρ_{ab}(T)$ display a 3D to 2D dimensional crossover when temperature decreases from $T_{c}$ to $T_{c0}$ and scaling near the $T_{c0}$ which we relate to the flux-flow and vortex-lattice melting. In the underdoped sample the vortices are effectively pinned by the random oxygen vacancies and the function $ρ_{ab}(T)$ in transitional region has smooth tails without any traces of crossover and scaling.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1191-1194
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Compression Changes in Electrical Resistance and Critical Temperature of $Nb_{1-x}Se_2Sn_x$ Single Crystals
Autorzy:
Obolenskiy, M.
Zavgorodniy, A.
Vovk, R.
Nazyrov, Z.
Goulatis, I.
Januszczyk, M.
Latosińska, J.
Powiązania:
https://bibliotekanauki.pl/articles/1419810.pdf
Data publikacji:
2012-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Fy
74.62.Fj
Opis:
In this work we investigate the influence of hydrostatic pressure (up to 12 kbar) on the critical parameters of $Nb_{1-x}Se_2Sn_x$ (x=0.1 and x=0.15) single crystals. It is shown that a change in the density of states at the Fermi level brings the main contribution to the increase in $T_{c}$ under pressure. Under the effect of hydrostatic pressure, the phonon spectrum is shifted to higher frequencies (narrowed). The estimated Debye temperature is consistent with those obtained from the heat capacity measurements in $NbSe_2$ single crystals. It is shown that upon increasing hydrostatic pressure the mean free path increases and $Nb_{1-x}Se_2Sn_x$ should be considered as the pure limit in the Ginzburg-Landau theory.
Źródło:
Acta Physica Polonica A; 2012, 122, 1; 159-161
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Properties of Normal and Superconducting States of Differently Doped REBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-x}$
Autorzy:
Sułkowski, C.
Powiązania:
https://bibliotekanauki.pl/articles/1933589.pdf
Data publikacji:
1995-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.72.-h
74.25.Fy
Opis:
Temperature dependence of resitivity, ρ(T), thermopower, S$\text{}_{300}$, superconducting transition temperature, T$\text{}_{c}$, and lower critical field, Η$\text{}_{c1}$(0), of differently doped REBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-x}$ ceramics have been measured. The hole doping of the CuO$\text{}_{2}$ plane is determined by the T$\text{}_{c}$, the oxygen concentration and/or the value of the thermopower. The temperature dependence of the resistivity above 200 K and the values of the lower critical field H$\text{}_{c1}$(0) show clear dependence on the hole concentration. Below 200 K, in contrast to simple metals, the resitivity of all samples decreases faster than linearly with the decreasing temperature. Classical electron-phonon scattering mechanism is not appropriate to describe the ρ(T) curves of REBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{7-x}$ compounds. Some observed features of the ρ(T) dependence are predicted by mean field phase diagram for the CuO$\text{}_{2}$ plane.
Źródło:
Acta Physica Polonica A; 1995, 88, 2; 375-380
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Van Hove Singularity and Superconductivity in Disordered Sr$\text{}_{2}$RuO$\text{}_{4}$
Autorzy:
Litak, G.
Annett, J. F.
Györffy, B. L.
Powiązania:
https://bibliotekanauki.pl/articles/2012935.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.62.Dh
74.25.Dw
74.25.Fy
Opis:
On the basis of a simple model we analyse the influence of disorder on critical temperature T$\text{}_{c}$ in p-wave superconductors. The disorder is treated by means of the coherent potential approximation and we focus our attention on the effect of a van Hove singularity near Fermi energy E$\text{}_{F}$. For the appropriate values of its parameters our model reproduces the experimentally found behaviour of Sr$\text{}_{2}$ RuO$\text{}_{4}$.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 249-252
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of the Granularity on the Transversal Resistance in Y_{0.55}Pr_{0.45}Ba_2Cu_3O_{7-δ} Superconductor
Autorzy:
da Luz, M.
dos Santos, C.
Machado, A.
Powiązania:
https://bibliotekanauki.pl/articles/1399293.pdf
Data publikacji:
2013-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.-q
74.25.Fy
74.81.Bd
Opis:
This work reports longitudinal $(R_{XX})$ and transverse $(R_{XY})$ resistance as a function of temperature measured at low magnetic fields for $Y_{0.55}Pr_{0.45}Ba_2Cu_3O_{7-δ}$ polycrystalline sample. It is observed non-zero transverse resistance at zero applied magnetic field below superconducting transition. The comparison between $R_{XX} (T)$ and $R_{XY} (T)$ curves demonstrate unambiguously that the transverse resistance is related to the double resistive superconducting transition in granular superconductors. I-V curves indicate that the transport properties of the investigated sample are in agreement with the predictions of the two-fluid model.
Źródło:
Acta Physica Polonica A; 2013, 124, 4; 702-705
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase-Slip Processes in Superconducting Films: AC Josephson Effect and New Phase Transition
Autorzy:
Dmitriev, V.
Zolochevskii, I.
Bezuglyi, E.
Kondrashev, D.
Powiązania:
https://bibliotekanauki.pl/articles/1812339.pdf
Data publikacji:
2008-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Fy
74.25.Nf
74.50.+r
Opis:
The resistive direct current state in wide thin superconducting films as the phase transition from superconducting to normal state is investigated in the absence of external magnetic field. We showed that the states of a wide film with increasing transport current appear in the following order: the superconducting state; the resistive vortex state; the critical state; the new vortex-free resistive state with phase-slip lines; the normal state. We detected the Shapiro current steps on the current-voltage characteristic of the wide film, which arise due to interaction of intrinsic Josephson radiation of phase-slip lines with external microwave irradiation.
Źródło:
Acta Physica Polonica A; 2008, 114, 1; 257-261
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dynamics of Hotspot Formation in Nanostructured Superconducting Stripes Excited with Single Photons
Autorzy:
Jukna, A.
Kitaygorsky, J.
Pan, D.
Cross, A.
Perlman, A.
Komissarov, I.
Sobolewski, R.
Okunev, O.
Smirnov, K.
Korneev, A.
Chulkova, G.
Milostnaya, I.
Voronov, B.
Gol'tsman, G.
Powiązania:
https://bibliotekanauki.pl/articles/1813380.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Fy
74.25.Sv
74.45.+c
Opis:
Dynamics of a resistive hotspot formation by near-infrared-wavelength single photons in nanowire-type superconducting NbN stripes was investigated. Numerical simulations of ultrafast thermalization of photon-excited nonequilibrium quasiparticles, their multiplication and out-diffusion from a site of the photon absorption demonstrate that 1.55 μm wavelength photons create in an ultrathin, two-dimensional superconducting film a resistive hotspot with the diameter which depends on the photon energy, and the nanowire temperature and biasing conditions. Our hotspot model indicates that under the subcritical current bias of the 2D stripe, the electric field penetrates the superconductor at the hotspot boundary, leading to suppression of the stripe superconducting properties and accelerated development of a voltage transient across the stripe.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 955-958
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
DC Characterization of the Coaxial Superconducting Cable
Autorzy:
Šouc, J.
Gömöry, F.
Vojenčiak, M.
Frolek, L.
Isfort, D.
Ehrenberg, J.
Bock, J.
Powiązania:
https://bibliotekanauki.pl/articles/1813698.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Sv
74.25.Fy
84.71.Mn
Opis:
Coaxial cable model with superconducting core and superconducting shield conductor was constructed and tested in DC regime. While the core was already examined in our previous works, in this contribution the detailed study of the superconducting shield conductor in DC conditions is presented. It consists of 16 ReBCO coated tapes with critical current 35 A each connected in parallel. Using shunts with known values placed in series the currents in individual tapes were possible to measure. Distribution of the total cable current into the individual tapes was monitored and its influence on critical current of the cable is discussed.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 375-378
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Ferromagnetic Layer on Critical Current of a Superconducting Wire
Autorzy:
Gömöry, F.
Vojenčiak, M.
Šouc, J.
Seiler, E.
Powiązania:
https://bibliotekanauki.pl/articles/1813946.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
41.20.Gz
74.25.Fy
74.25.Nf
Opis:
We investigated how a 10-50 μm layer from soft ferromagnetic material, incorporated in the architecture of a composite superconducting tape, could influence the capability of the tape to transport electrical current. Numerical procedure was developed to calculate the local distribution of magnetic field and current in the condition when all the superconductor is carrying its critical current density. It was found that the concentration of magnetic flux in ferromagnetic layers allows to reduce the local value of magnetic flux density felt by the superconductor. In this way, the critical current of the tape in low applied magnetic fields can be improved. This theoretical prediction is confirmed by experimental observation.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 605-608
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermoelectric Power of $MgB_2$ Single Crystals Doped with Holes and Electrons
Autorzy:
Oganisian, K.
Rogacki, K.
Sulkowski, C.
Zhigadlo, N.
Katrych, S.
Karpinski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1812320.pdf
Data publikacji:
2008-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Fy
74.70.Ad
74.62.Dh
Opis:
The thermoelectric power of $MgB_2$ single crystals, non-substituted, single-substituted with C, and co-substituted with C and Li, was investigated in the temperature range from 10 to 300 K. Both the in-plane $(S_ab)$ and the out-of-plane $(S_c)$ thermoelectric powers are positive for non-substituted crystals and both $S_{ab}$ and $S_c$ change a sign for crystals doped with electrons when C is substituted for B in the amount larger than 6 at.%. The substitution of C, which supplies electrons mainly into the σ band, reduces the thermoelectric power anisotropy, most likely by increasing the interband scattering. When Li is additionally co-substituted for Mg, $S_ab$ remains unchanged but $S_c$ increases substantially. The Li substitution donates holes into the π band rather than into the σ band and in this way modifies the π band properties, including the possible increase in the intraband scattering.
Źródło:
Acta Physica Polonica A; 2008, 114, 1; 191-195
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Asymmetric Tunneling Conductance in Doped Antiferromagnets
Autorzy:
Maciąg, A.
Wróbel, P.
Powiązania:
https://bibliotekanauki.pl/articles/2046776.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
74.20.Mn
74.25.Fy
Opis:
We calculate the tunneling conductance in the framework of the spin polaron model, which is an effective model for the t-J model, in the limit where at least short-range antiferromagnetic correlations exist. We show that both in the normal state and in the superconducting state the asymmetry of tunneling conductance is present. This fact is the implication of the particle-hole asymmetry of the spin polaron Hamiltonian in the limit of low density of spin polarons which are quasiparticles emerging in a hole doped antiferromagnet. Experimental evidence of analogous asymmetric tunneling conductance was found in the tunneling spectroscopy measurements of high T$\text{}_{c}$ superconductors.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 607-610
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Negative Magnetoresistance in the Variable-Range-Hopping Transport of Strongly Underdoped La$\text{}_{2-x}$Sr$\text{}_{x}$CuO$\text{}_{4}$
Autorzy:
Malinowski, A.
Cieplak, M. Z.
Berkowski, M.
Guha, S.
Powiązania:
https://bibliotekanauki.pl/articles/2046779.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.72.-h
74.25.Fy
73.43.Qt
Opis:
The in-plane transport of strongly underdoped La$\text{}_{2-x}$Sr$\text{}_{x}$CuO$\text{}_{4}$ 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$\text{}_{F}$)=N$\text{}_{0}$ (E-E$\text{}_{F}$)$\text{}^{p}$, with a small exponent p of the order of 0.1. In the magnetic field parallel to CuO$\text{}_{2}$ planes one of the variable-range-hopping parameter,ρ$\text{}_{0}$, increases by about 20-25%, while the other one, T$\text{}_{0}$, 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.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 611-615
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Metal-Insulator Transition in Zinc-Doped LaSrCuO
Autorzy:
Malinowski, A.
Cieplak, M. Z.
Berkowski, M.
Plesiewicz, W.
Skośkiewicz, T.
Powiązania:
https://bibliotekanauki.pl/articles/2046782.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.72.-h
71.30.+h
74.25.Fy
Opis:
The magnetotransport in the vicinity of the metal-insulator transition in La$\text{}_{1.85}$Sr$\text{}_{0.15}$Cu$\text{}_{x}$Zn$\text{}_{1-x}$O$\text{}_{4}$ 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$\text{}_{2-x}$Sr$\text{}_{x}$CuO$\text{}_{4}$. 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.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 617-621
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of Europium-Barium Nonstoichiometry in EBCO123 Systems on Transition and Magnetization Properties
Autorzy:
Cigáň, A.
Maňka, J.
Kopčok, M.
Polovková, J.
Jurdák, P.
Koňakovský, A.
Powiązania:
https://bibliotekanauki.pl/articles/1813614.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.72.-h
74.62.Bf
74.25.Fy
74.25.Ha
Opis:
We studied the effects of Eu-Ba nonstoichiometry in two series of $Eu_{1+x}Ba_{2-x}Cu_3O_{7-δ}$ and $Eu_{1-x}Ba_{2+x}Cu_3O_{7-δ}$ samples on transition, structural, and magnetic properties. The samples with the nominal composition of 0≤x≤0.07 were synthesized by the solid-state reaction method from $Eu_2O_3,$ $BaCO_3,$ and CuO precursors and sintered at 1050°C for 72 h in flowing oxygen. All the samples show the values of critical temperature $T_c$, volume density ρ, and maximum volume magnetization $M_\text{max}$ higher than 90 K, 6.3 g $cm^{-3}$ and $10^4 Am^{-1}$, respectively, except for x = 0.07 samples. The Eu-Ba nonstoichiometry in the two series shows different effects on transport, magnetization hystereses, and intergrain properties of the samples.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 219-222
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of DC Magnetic Field on AC Loss of YBCO Coated Conductor with Ferromagnetic Substrate
Autorzy:
Vojenčiak, M.
Šouc, J.
Gömöry, F.
Seiler, E.
Powiązania:
https://bibliotekanauki.pl/articles/1813686.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Fy
74.25.Nf
74.78.Bz
75.50.-y
Opis:
Most of YBCO tape conductors are prepared on a ferromagnetic substrate. The ferromagnetic material is then exposed to the self magnetic field of the superconductor and also to external magnetic field. In AC magnetic field hysteretic and eddy current losses are generated in the substrate. In this work the AC transport loss of an YBCO coated conductor on a ferromagnetic substrate was measured using electromagnetic method. There are two contributions to total loss - a loss in the superconductor and a loss in the substrate. To suppress the hysteretic loss in the substrate, it is possible to saturate it using DC magnetic field. In this regime significant decrease in total loss was observed.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 359-362
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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