F. Rullier-Albenque

Defect production rates in normal and in superconducting states

Abstract Electronic thermal conductivity of metals is different in normal (N) and superconducting (S) states. An experiment is described in which various metals (Nb, V, Pb) are irradiated with fast neutrons or with uranium fission fragments, alternatively in (N) and in (S) state at constant temperature. The damage rate is the same in both eases, showing that electronic thermal conductivity does not influence significantly the damage rate.

Irradiation of YBa2Cu3O7−δ single crystals by 5.6 GeV xenon ions

Abstract Single crystals of YBa2Cu3O7−δ were irradiated at 95 K by 5.6 GeV Xe ions and the evolutions of the superconducting resistive curves - measured parallel and perpendicular to the c axis - were determined in situ as a function of ion fluences. We find that ϱc and ϱab increase linearly with the fluence and even tend to saturate for the highest fluences. This behaviour strongly differs from that found for sintered samples irradiated under the same conditions for which a quasi-exponential increase of resistance was observed. Nevertheless our results confirm that energy deposition by electronic excitation plays a role in defect creation as previously reported in Xe irradiated sintered samples.

Effects of low temperature electron irradiation on single crystal and sintered YBa2Cu3O7−δ

Abstract Sintered samples and single crystals of YBa 2 Cu 3 O 7-δ have been irradiated at low temperature by 2.5 MeV electrons. Under irradiation the critical temperature T c decreases and the normal state resistance R increases. The ΔT c versus ΔR variations are nearly the same in single crystal as in sintered samples, indicating that degradations of T c and R result mostly from intragrain disorder. The evolution of the transport critical current j c of sintered YBa 2 Cu 3 O 7 measured in situ as a function of electron fluence show that weak links between grains are also damaged by irradiation defects. We also found that decrease rates of T c are higher in samples with lower initial values of T c . This behaviour is not restricted to YBa 2 Cu 3 O 7−δ but seems to be quite general in high- T c oxides.

Effect of electron irradiation in Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 superconductors

Abstract The effect of electron-irradiation induced defects on the superconducting transition temperature ( T c ), on the normal-state resistivity and the stability of defects on thermal cycling were studied in Bi 2 Sr 2 CaCu 2 O 8 and Bi 2 Sr 2 CuO 6 superconductors. It was found that T c / T c0 is about three times less sensitive to irradiation-induced defects in the former than in the latter compound. We show that the ab plane resistivity increase in both compounds is due to the decrease of the mean free path caused by defects created in the CuO 2 planes. The defects start to anneal above 100 K and, at 300 K; only 50% of the low-temperature defect concentration is left.

Irreversibility line in YBa2Cu3O7 samples: A comparison between experimental techniques and effect of electron irradiation

Abstract We have investigated the irreversibility line (IRL) of a ceramic YBa 2 Cu 3 O 7 sample by probing the onset of irreversibility in four DC and AC techniques. All techniques yield a line which obeys a power law H=A( 1−T T c ) n but A and n depend on the technique. Also, the location of the peak in the AC signal obeys this power-law but it does not scale with the onset of irreversibility. We have also investigated the effect of two doses of 2.5 MeV electron irradiation on the IRL and find that after irradiation both the transition temperature T c and the irreversibility temperature T irr decrease. The decrease in T irr scales with the decrease in T c . We propose that this scaling indicates that electron-irradiation does not induce pinning centers stronger than those present in the unirradiated sample.

Flux pinning enhancement near Tc in YBa2Cu3O7 crystals irradiated by 5.3 GeV Pb ions

Abstract We have studied the effect of 5.3 GeV Pb irradiation on irreversible magnetic properties of YBa 2 Cu 3 O 7 crystal, using an ultra-sensitive local Hall-probe technique. In this article we briefly summarize our previous results and present new data at 90 K (=0.97 T c ) which demonstrate that this type of irradiation enhances flux pinning in the vicinity of T c .

Universal Tc depression by irradiation defects in underdoped and overdoped cuprates

We report on a study of the influence of defects introduced in the CuO2 planes of cuprates in a wide range of hole dopings x. Tc and electrical resistivity ρ(T) measurements have been performed on electron-irradiated YBa2Cu3O7 − δ and Tl2Ba2CuO6 + x single crystals. A universal scaling between the decrease in Tc and Δρ2D×n, where Δρ2D is the increase of the 2D resistance induced by the defects and n is the carrier concentration equal to x, is found for all the samples investigated here. This demonstrates that the hole content is the relevant parameter to describe the transport properties all over the phase diagram, in contradiction with a recent suggestion of a change in the number of carriers from x to 1 − x at the optimal doping. Moreover, the analysis of our data suggests that strong scattering persists on the overdoped side.-2

Effect of controlled disorder on quasiparticle thermal transport inBi2Sr2CaCu2O8

Low temperature thermal conductivity,

Anisotropic electrical properties of superconducting single crystals YBa2Cu3O7−x

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An experimental argument — in Nb3Ge — for the Labbé-Barisic-Friedel theory of A-15 superconductors

, of optimally-doped Bi2212 was studied before and after the introduction of point defects by electron irradiation. The amplitude of the linear component of