The effect of low-temperature electron irradiation on the transition temperature of YBa2Cu3O7−δ superconductors
01 Mar 1988-European Physical Journal B (Springer Science and Business Media LLC)-Vol. 71, Iss: 1, pp 37-42
TL;DR: In this article, the complex susceptibility χ=χ′−iχ″ of electron-irradiated YBa2Cu3O7−δ showed a strong influence of the electron irradiation dose, Φ·t on the transition temperatureTc.
Abstract: Measurements of the complex susceptibility χ=χ′−iχ″ of electron-irradiated YBa2Cu3O7−δ show a strong influence of the electron irradiation dose, Φ·t on the transition temperatureTc. For irradiation doses of Φ·t=2.2·1019 e−/cm2 we find a damage rate of ΔTc/Δ(Φ·t)=−1.6·10−19 K/(e−/cm2). It is assumed that the decrease ofTc is mainly a bulk effect due to the production of atomic defects like vacancies and interstitials in the Cu−O−Cu chains and in the basal planes of the unit cells.
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TL;DR: In this paper, the particle-induced depression of the superconducting critical temperature Tc of YBa2Cu3O7−δ is shown to be directly proportional to the nonionizing energy deposited in the lattice by primary knock-on atoms displaced by incident electrons, protons, and heavy ions.
Abstract: The particle‐induced depression of the superconducting critical temperature Tc of YBa2Cu3O7−δ is shown to be directly proportional, over seven orders of magnitude, to the nonionizing energy deposited in the lattice by primary knock‐on atoms displaced by incident electrons, protons, and heavy ions. It is concluded that ΔTc is proportional only to the average number of defects produced and can therefore be predicted for any particle, energy, and fluence from a calculation of the nonionizing energy loss.
86 citations
TL;DR: In this article, sintered compacts of YBa/sub 2/Cu/sub 3/O/sub 7/ were prepared with uranium additions of 150 and 380 atomic ppm and exposed to thermal neutron fluences of 4.5, 63, and 77 K, respectively.
Abstract: To assess fission-fragment damage as flux-pinning centers, sintered compacts of YBa/sub 2/Cu/sub 3/O/sub 7/ were prepared with uranium additions of 150 and 380 atomic ppm and exposed to thermal neutron fluences of 4.3/times/10/sup 17/, 1.2/times/10/sup 18/, and 4.0/times/10/sup 18//cm/sup 2/. Magnetic hysteresis measurements were made as functions of temperature at fields up to 2.5 T. The hysteresis at 1 T for the sample containing 150 ppm uranium increased upon an irradiation of 1.2/times/10/sup 18//cm/sup 2/ by 3.7 times at 4.5 K, 20 times at 63 K, and 8.3 times at 77 K. Much smaller increases in magnetic hysteresis were observed in undoped samples exposed to thermal neutrons. Critical-current densities were calculated from the hysteresis observed at 1 T using the critical-state model, assuming the currents to be restricted to the grains (/approx/5 /mu/m radius). For the 150 ppm, 1.2/times/10/sup 18//cm/sup 2/ sample, the 1-T intragranular critical-current densities obtained are 1.5/times/10/sup 7/, 1.0/times/10/sup 6/, and 1.4/times/10/sup 5/ A/cm/sup 2/ at temperatures of 4.5, 63, and 77 K, respectively. The critical temperatures by an ac susceptibility technique showed that the 4/times/10/sup 18//cm/sup 2/ irradiation lowered the onset critical temperatures only slightly, from 91 to 90 K and from 91.5 to 89 Kmore » for the 150 and 380 ppm samples, respectively.« less
69 citations
TL;DR: In this article, the penetration of the Shubnikov phase into both single-crystal and sintered YBaCuO specimens has been observed by means of the magneto-optical Faraday effect using the high Verdet constant in thin evaporated films of a mixture of EuS and EuF 2.
Abstract: The penetration of the Shubnikov phase into both single-crystal and sintered YBaCuO specimens has been observed by means of the magneto-optical Faraday effect using the high Verdet constant in thin evaporated films of a mixture of EuS and EuF 2 . This method allows the direct observation of the flux motion. After cycling magnetic field from zero, the trapped flux structure in the single crystal consists of large domains which are related to the sample shape, whereas in sintered specimens only a part of the total number of the grains transforms into the Shubnikov phase.
43 citations
TL;DR: A comprehensive survey on intensive studies performed during the last decades on point defect reactions on α‐iron (α‐Fe) and its diluted alloys is presented, revealing in great detail the underlying intrinsic reactions of the radiation‐induced defects.
Abstract: This review presents a comprehensive survey on intensive studies performed during the last decades on point defect reactions on α-iron (a-Fe) and its diluted alloys. Our intention is to give an actual account of the knowledge accumulated on this subject, as it has been obtained predominantly by means of the magnetic after-effect (MAE) spectroscopy. After a concise introduction into the theoretical and experimental fundamentals of this technique, the main concern is focused on the presentation and detailed discussion of the MAE spectra arising - after low-temperature electron (e - )- or neutron(n)-irradiation and subsequent annealing - in: (i) high-purity α-Fe and α-Fe doped with (ii) substitutional solutes (like Ni, V, Al, Cu, Ti, Be, Si, Mn,...) or (iii) interstitial solutes (like O, H, C, N). During the course of systematic annealing treatments, these respective spectra undergo dramatic variations at specific temperatures thereby revealing in great detail the underlying intrinsic reactions of the radiation-induced defects, i.e., reorientation, migration, clustering, dissolution and finally annihilation. In alloyed Fe systems the corresponding reaction sequences are even multiplied due to additional interactions between defects and solute atoms. Most valuable information concerning formation-, dissociation- and binding enthalpies of small, mixed clusters (of the type C i V k , N i V k ; i, k ≥ 1) has been obtained in high-purity α-Fe base material which, after charging with C or N, had been e -irradiated. Concerning the basic recovery mechanisms in α-Fe, two complementary results are obtained from the analysis of the various systems: (i) in high-purity and substitutionally alloyed α-Fe the recovery in Stage-III (200 K) is governed by a three-dimensionally migrating (H I M = 0.56 eV) stable interstitial (dumbbell); (ii) following the formation and dissociation kinetics of small clusters (C 1 V k , N 1 V k ) in interstitially alloyed α-Fe the migration enthalpy of the monovacancy must hold the following relation H N M (0.76 eV) < H C M (0.84 eV) < H V1 M . These results are in clear agreement with the socalled two-interstitial model (2IM) in α-Fe - a conclusion being further substantiated by a systematic comparison with the results obtained from nonrelaxational techniques, like i.e. positron annihilation (PA), which by their authors are preferentially interpreted in terms of the one-interstitial model (1IM).
39 citations
TL;DR: In this article, extensive measurements of magnetic hysteresis loops of YBa 2 Cu 3 O 7- δ polycrystals have been carried out and the results are discussed within the framework of the critical state model in order to determine the volume pinning force F p and the critical current density j c.
Abstract: Extensive measurements of magnetic hysteresis loops of YBa 2 Cu 3 O 7- δ polycrystals have been carried out presenting a survey of the magnetic properties of this material. The results are discussed within the framework of the critical state model in order to determine the volume pinning force F p and the critical current density j c . Two different point defect structures induced by low temperature electron irradiation and successive annealing experiments were examined. Although both treatments mainly change the oxygen arrangement, only the electron irradiation caused an enhancement of the critical current.
31 citations
References
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IBM1
TL;DR: In this paper, Ba−La−Cu−O system, with the composition BaxLa5−xCu5O5(3−y) have been prepared in polycrystalline form, and samples with x=1 and 0.75,y>0, annealed below 900°C under reducing conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound.
Abstract: Metallic, oxygen-deficient compounds in the Ba−La−Cu−O system, with the composition BaxLa5−xCu5O5(3−y) have been prepared in polycrystalline form. Samples withx=1 and 0.75,y>0, annealed below 900°C under reducing conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound. Upon cooling, the samples show a linear decrease in resistivity, then an approximately logarithmic increase, interpreted as a beginning of localization. Finally an abrupt decrease by up to three orders of magnitude occurs, reminiscent of the onset of percolative superconductivity. The highest onset temperature is observed in the 30 K range. It is markedly reduced by high current densities. Thus, it results partially from the percolative nature, bute possibly also from 2D superconducting fluctuations of double perovskite layers of one of the phases present.
10,272 citations
TL;DR: The oxide superconductors, particularly those recently discovered that are based on La2CuO4, have a set of peculiarities that suggest a common, unique mechanism: they tend in every case to occur near a metal-insulator transition into an odd-electron insulator with peculiar magnetic properties.
Abstract: The oxide superconductors, particularly those recently discovered that are based on La2CuO4have a set of peculiarities that suggest a common, unique mechanism: they tend in every case to occur near a metal-insulator transition into an odd-electron insulator with peculiar magnetic properties. This insulating phase is proposed to be the long-sought “resonating-valence-bond” state or “quantum spin liquid” hypothesized in 1973. This insulating magnetic phase is favored by low spin, low dimensionality, and magnetic frustration. The preexisting magnetic singlet pairs of the insulating state become charged superconducting pairs when the insulator is doped sufficiently strongly. The mechanism for superconductivity is hence predominantly electronic and magnetic, although weak phonon interactions may favor the state. Many unusual properties are predicted, especially of the insulating state.
5,409 citations
TL;DR: Structural, magnetic, and electronic properties of compounds in the series La2-xSrx CuO4-y for 0.05 ≤ x ≤ 1.1, with δx = 0.025, revealed superconductivity among several members of the series.
Abstract: Structural, magnetic, and electronic properties of compounds in the series La 2- x Sr x CuO 4- y for 0.05 ≤ x ≤ 1.1, with δ x = 0.025, were studied. Resistance, susceptibility, Meissner, and shielding measurements have revealed superconductivity among several members of the series. For x = 0.15, the transition temperature T c , measured at the midpoint of the resistive transition, is a maximum at 39.3 K with a width of 2 K. At other compositions the transition is broader and occurs at a lower temperature. Annealing the x = 0.15 sample in oxygen at 500°C increases T c to 40.3 K, while annealing at the same temperature under vacuum suppresses the superconductivity. These changes in oxygen content and T c are reversible.
270 citations
TL;DR: In this paper, it was suggested that the high T c is due to scattering of electrons from such resonances rather than from photons, and the newly discovered high Tc oxide metals have a low enough electron density that the charge transfer excitations between the nearest neighbor cations and anions are unscreened.
208 citations