P. Schüle

Bio: P. Schüle is an academic researcher from Max Planck Society. The author has contributed to research in topics: Irradiation & Electron beam processing. The author has an hindex of 3, co-authored 3 publications receiving 59 citations.

The effect of low-temperature electron irradiation on the transition temperature of YBa2Cu3O7−δ superconductors

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.

Pair breaking effects of atomic disorder induced in YBa2Cu3O7 by electron irradiation

Abstract: Irradiation effects of electrons at very low temperatures (Tirr<40 K, 2.7 MeV) on the DC-susceptibility χDC above Tc of YBa2Cu3O7 have been studied by means of a SHE SQUID magnetometer. Contrary to nonirradiated stoichiometric samples which have a nearly temperature independent paramagnetic susceptibility, χDC, between 100°C and 300°C, specimens irradiated with doses of 4 × 1019 e-/cm2 show a distinct Curie-type behaviour due to the formation of local magnetic moments, superimposed on a temperature independent part. By annealing up to temperatures of 500 K recovering of the Curie-type contribution takes place in a similar way as that of Tc. The Pauli susceptibility remains constant during irradiation, indicating that there is, contrary to A15-superconductors, no significant reduction of the density of states at the Fermi level. The correlated annealing of Tc and of the Curie constant suggests a magnetic pair breaking mechanism due to radiation induced local magnetic moment.

The influence of the disorder induced by electron irradiation on Tc and magnetic susceptibility of YBa2Cu3O7

Abstract: The radiation dose dependence of Tc for sintered YBa2Cu3O7 irradiated with 2.7 MeV-electrons at very low temperatures (Tirr < 40 K) is recorded by AC magnetic susceptibility measurements. During irradiation, Tc shifts linearly with dose from 92 K down to 77 K at a dose of 3.8 · 10−19 e−/cm2. The shape of the transition is not significantly influenced by the irradiation. A big part of the radiation damage recovers during tempering up to RT with a distinct step at 180K. The high sensitivity to irradiation is not explainable only by the displacement of O-Atoms, but suggests that also Cu-sites of the CuOCuOchains are affected.

Effect of particle-induced displacements on the critical temperature of YBa2Cu3O7−δ

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.

Increased flux pinning upon thermal-neutron irradiation of uranium-doped YBa/sub 2/Cu/sub 3/O/sub 7/

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

Observation of flux penetration in YBa2Cu3O7−δ superconductors by means of the magneto-optical Faraday effect

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.

Defect phenomena in superconducting oxides and analogous ceramic oxides

Abstract: The authors discuss the defect phenomena in superconducting oxides. They survey those aspects of oxide superconductors which relate them most closely to conventional ceramic oxides, concentrating on processes and behaviour related to defects. They also identify areas of difference between two types of oxide. Theoretical modelling of conventional oxides has been extremely effective, and they emphasize that some of these modelling tools can be exploited for the superconducting oxides too. In particular, they stress those methods and ideas that provide a framework for understanding behaviour, those that provide a database of good quantitative experiments and those that provide an established and tested approach to quantitative modelling as a guide to prediction, optimization and extrapolation. Much progress has been made in both theory and experiment, but some problems do remain and these have not been omitted from the discussions. There is potential to exploit past work on defects in oxides, so as to control defect processes and microstructure and hence to enhance performance.

A Review of the Magnetic Relaxation and Its Application to the Study of Atomic Defects in α-Iron and Its Diluted Alloys.

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).