Effect of damage by 2 MeV He ions and annealing on Hc2 in MgB2 thin films

Gandikota, R.; Singh, Rakesh Kumar; Kim, J.; Wilkens, B. J.; Newman, Nathan; Rowell, J. M.; Pogrebnyakov, A. V.; Xi, X. X.; Redwing, Joan M.; Xu, Shengyong; Li, Q.; Moeckly, B. H.

doi:10.1063/1.2012524

Cited by 38 publications

(77 citation statements)

References 19 publications

(31 reference statements)

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“…The defects induced by neutron irradiation act as inter-and intra-band scattering centers; the intraband scattering causes a reduction of the electron mean free path and is responsible for the growth of the normalstate resistivity. The reduction of T c has been ascribed to both the scattering processes and the smearing of the electron density of states near the Fermi surface [11,13].…”

Section: Experimental Apparatus and Samplesmentioning

confidence: 99%

“…In order to carry out investigation on this topic, essentially two methods have been used to insert defects and/or disorder in MgB 2 : chemical substitution and damage by irradiation [9,10,11,12,13]. In any cases, the inclusion of defects, besides to change the inter-band scattering, might increase the upper critical field and the critical current, strongly affecting the fluxon dynamics.…”

Section: Introductionmentioning

confidence: 99%

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Microwave surface resistance of pristine and neutron-irradiated MgB2 samples in magnetic field

et al. 2008

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Abstract. We report on the microwave surface resistance of two polycrystalline Mg 11 B2 samples; one consists of pristine material, the other has been irradiated at very high neutron fluence. It has already been reported that in the strongly irradiated sample the two gaps merge into a single value. The mw surface resistance has been measured in the linear regime as a function of the temperature and the DC magnetic field, at increasing and decreasing fields. The results obtained in the strongly irradiated sample are quite well justified in the framework of a generalized Coffey and Clem model, in which we take into account the field distribution inside the sample due to the critical state. The results obtained in the pristine sample show several anomalies, especially at low temperatures, which cannot be justified in the framework of standard models for the fluxon dynamics. Only at temperatures near Tc and for magnetic fields greater than 0.5Hc2(T ) the experimental data can quantitatively be accounted for by the Coffey and Clem model, provided that the upper-critical-field anisotropy is taken into due account. PACS

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Section: Experimental Apparatus and Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microwave surface resistance of pristine and neutron-irradiated MgB2 samples in magnetic field

et al. 2008

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“…For example, the ρ 40 can be corrected by a factor that represents the aerial currentcarrying fraction (γ = ρ 40 / ρ 40,ideal ≅ ρ 40 / 7.4 μΩ.cm) [6,7] to obtain a ρ 40K,corrected that is characteristic of the intra-granular resistivity alone. Measurements of T c and the corrected value of the residual resistivity of MgB 2 , after both ion and neutron irradiation [6,8] suggest a universal linear dependence, with T c extrapolating to 0 K for ρ 40k,corrected values of ~90 μΩ.cm.…”

Section: Effect On Critical Current and Slope Of Upper Critical Fieldmentioning

confidence: 99%

Effect of Rb and Cs doping on superconducting properties of MgB₂thin films

Singh¹,

Shen

Gandikota

et al. 2008

Supercond. Sci. Technol.

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Abstract. Our Rutherford backscattering spectrometry (RBS) study has found that concentrations up to 7 atomic % of Rb and Cs can be introduced to a depth of ~700 Å in MgB 2 thin films by annealing in quartz ampoules containing elemental alkali metals at <350 o C. No significant change in transition temperature (T c ) was observed, in contrast to an earlier report of very high T c (>50 K) for similar experiments on MgB 2 powders. The lack of a significant change in T c and intra-granular carrier scattering suggests that Rb and Cs diffuse into the film, but do not enter the grains. Instead, the observed changes in the electrical properties, including a significant drop in J c and an increase in Δρ (ρ 300 -ρ 40 ), arise from a decrease in inter-granular connectivity due to segregation of the heavy alkaline metals and other impurities (i.e. C and O) introduced into the grain boundary regions during the anneals.

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“…Unfortunately, substitutional defects introduce charge doping, which complicates the understanding of the role of IBS itself. In this respect, irradiation with neutrons 9, , , , 10 11 12 13 and alpha particles 14,15 is very appealing since it produces homogeneous defect structures, without introducing charge doping. With increasing irradiation resistivity increases monotonously and T c decreases correspondingly; in heavily irradiated samples superconductivity is completely suppressed.…”

mentioning

confidence: 99%

Intraband vs. interband scattering rate effects in neutron irradiated MgB ₂

Putti¹,

Brotto²,

Monni³

et al. 2007

Europhys. Lett.

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One of the most important predictions of the two-gap theory of superconductivity concerns the role of interband scattering (IBS) by impurities. IBS is expected to decrease the critical temperature, T c , of MgB 2 to a saturation value of about 20 K, where the two gaps merge to a single one. These predictions have been partially contradicted by experiments. In fact, T c does not saturate in irradiated samples, but decreases linearly with residual resistivity and the merging of the gaps has been observed at a much lower T c (11 K). In this paper we argue that, while at low level of disorder IBS is the leading mechanism that suppresses superconductivity, at higher disorder the experimental results can only be understood if the smearing of the density of states due to intraband electron lifetime effects is considered.

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Effect of damage by 2 MeV He ions and annealing on Hc2 in MgB2 thin films

Abstract: a) J. Kim, a) B. Wilkens, b) N. Newman, a),b),g) J.M. Rowell, a) A.V. Pogrebnyakov, c),d),e) X.X. Xi, c),d),e) J.M. Redwing, d),e) S.Y. Xu, c),e) Qi Li, c),e) and B.H. Moeckly f)

Cited by 38 publications

References 19 publications

Microwave surface resistance of pristine and neutron-irradiated MgB2 samples in magnetic field

Microwave surface resistance of pristine and neutron-irradiated MgB2 samples in magnetic field

Effect of Rb and Cs doping on superconducting properties of MgB₂thin films

Intraband vs. interband scattering rate effects in neutron irradiated MgB ₂

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Effect of damage by 2 MeV He ions and annealing on Hc2 in MgB2 thin films

Abstract: a) J. Kim, a) B. Wilkens, b) N. Newman, a),b),g) J.M. Rowell, a) A.V. Pogrebnyakov, c),d),e) X.X. Xi, c),d),e) J.M. Redwing, d),e) S.Y. Xu, c),e) Qi Li, c),e) and B.H. Moeckly f)

Cited by 38 publications

References 19 publications

Microwave surface resistance of pristine and neutron-irradiated MgB2 samples in magnetic field

Microwave surface resistance of pristine and neutron-irradiated MgB2 samples in magnetic field

Effect of Rb and Cs doping on superconducting properties of MgB2thin films

Intraband vs. interband scattering rate effects in neutron irradiated MgB 2

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Product

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Effect of Rb and Cs doping on superconducting properties of MgB₂thin films

Intraband vs. interband scattering rate effects in neutron irradiated MgB ₂