New Fe-based superconductors: properties relevant for applications

Putti, M.; Pallecchi, I.; Bellingeri, E.; Cimberle, M. R.; Tropeano, M.; Ferdeghini, C.; Palenzona, A.; Tarantini, C.; Yamamoto, Akiyasu; Jiang, J.; Jaroszyński, J.; Kametani, F.; Abraimov, D.; Polyanskii, Anatolii; Weiss, Jeremy; Hellstrom, E. E.; Gurevich, A.; Larbalestier, D. C.; Jin, R.; Sales, B. C.; Sefat, Athena S.; McGuire, Michael A.; Mandrus, David; Cheng, Peng; Jia, Ying; Wen, Hao; Lee, Sanghan; Eom, C. B.

doi:10.1088/0953-2048/23/3/034003

Cited by 278 publications

(297 citation statements)

References 65 publications

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“…24 The initial slope for Sr 0.6 K 0.4 Fe 1.95 Co 0.05 As 2 instead is with −5.5 T K −1 a typical value for this class of materials. 22,25 The Werthammer-Helfand-Hohenberg (WHH) model 26,27 is commonly used to evaluate the T = 0 limit of the upper critical field, H 0 c2 . Accounting only for orbital effects where the Maki parameter α is 0, the break-down of SC is predicted for…”

Section: Resultsmentioning

confidence: 99%

Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors

Weickert

Schnelle

Wosnitza

et al. 2011

Journal of Applied Physics

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We present the first study of codoped iron-arsenide superconductors of the 122 family (Sr/Ba) 1−x K x Fe 2−y Co y As 2 with the purpose to increase the upper critical field H c2 compared to single doped Sr/BaFe 2 As 2 materials. H c2 was investigated by measuring the magnetoresistance in high pulsed magnetic fields up to 64 T. We find, that H c2 extrapolated to T = 0 is indeed enhanced significantly to ≈ 90 T for polycrystalline samples of Ba 0.55 K 0.45 Fe 1.95 Co 0.05 As 2 compared to ≈ 75 T for Ba 0.55 K 0.45 Fe 2 As 2 and BaFe 1.8 Co 0.2 As 2 single crystals. Codoping thus is a promising way for the systematic optimization of iron-arsenic based superconductors for magnetic-field and high-current applications.

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Section: Resultsmentioning

confidence: 99%

Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors

Weickert

Schnelle

Wosnitza

et al. 2011

Journal of Applied Physics

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“…In addition to T c , these iron based superconductors were reported to have a very high upper critical field, B c2 , and low B c2 anisotropy, making them potential candidates for a wide array of future applications [8][9][10][11]. The early results indicate that the global critical current is limited by intergrain currents over the grain boundaries in polycrystalline bulk and wires [12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

High transport critical current densities in textured Fe-sheathed Sr1−xKxFe2As2+Sn superconducting tapes

Gao

Wang

Yao

et al. 2011

Applied Physics Letters

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Abstract:We report the realization of grain alignment in Sn-added Sr 1-x K x Fe 2 As 2 superconducting tapes with Fe sheath prepared by ex-situ powder-in-tube method. At 4.2 K, high transport critical current densities J c of 2.5×10 4 A/cm 2 (I c = 180 A) in self-field and 3.5×10 3 A/cm 2 (I c = 25.5 A) in 10 T have been measured. These values are the highest ever reported so far for Fe-based superconducting wires and tapes. We believe the superior J c in our tape samples are due to well textured grains and strengthened intergrain coupling achieved by Sn addition. Our results demonstrated an encouraging prospect for application of iron based superconductors.* Author to whom correspondence should be addressed; E-mail: ywma@mail.iee.ac.cn 2 The discovery of superconductivity in LaFeAsO 1-x F x and related compounds, with a higher transition temperature, T c of ~55 K, has triggered great research interests from both theoretical and applied aspects [1][2][3][4][5][6][7]. In addition to T c , these iron based superconductors were reported to have a very high upper critical field, B c2 , and low B c2 anisotropy, making them potential candidates for a wide array of future applications [8][9][10][11]. The early results indicate that the global critical current is limited by intergrain currents over the grain boundaries in polycrystalline bulk and wires [12][13][14][15][16][17][18]. Recent experiments revealed that high-angle grain boundary largely deteriorates critical current density J c in Ba(Fe 1-x Co x ) 2 As 2 bicrystals [19,20]. These results suggest that the discovered iron based superconductors are exhibiting weak link grain boundary behavior similar to high-T c cuprate superconductors. An effective method to overcome the weak link problem is to engineering textured grains in iron based superconductors to minimize deterioration of the critical current density across high-angle grain boundaries.Recently Co-doped Ba122 coated conductors have been grown by several groups utilizing the existing YBCO coated conductor technology and have reached a self-field J c over 1 MA/cm 2 [21][22][23]. However, the technology has the shortcoming of low production rate, complexity and high equipment cost. Furthermore, it is hard to be applied to the volatile elements in iron based superconductors such as alkali metals doped 122 phase and F doped 1111 phase. Cold deformation process is a well-developed technique used to enhance the degree of grain alignment and critical current density of Bi2223 superconductors [24,25]. It is unsurprising that this technique may also be suitable for iron based superconductors too. Besides grain alignment, adding metallic elements is another effective way to improve the grain connectivity of the iron based superconductors. For example, we have reported that the superconducting properties of the 122 phase iron based superconductor can be significantly increased by Ag or Pb addition [26,27]. Recently Togano et al [28] reported further improvement in transport critical current in the Ba122 wires with A...

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“…These favorable characteristics make it urgent to explore their potential for applications with the hope that practical conductors can be made with these Fe-based superconductors using simpler processes than are needed with high-temperature cuprate superconductors. 8 Actually these new Fe-based superconductors share several characteristics with cuprates including: layered structures, coexistence of different orderings, occurrence of superconductivity upon doping, short coherence length and unconventional pairing. In cuprates all these features have been shown to be unfavorable for applications.…”

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confidence: 99%

Evidence for electromagnetic granularity in polycrystalline Sm1111 iron-pnictides with enhanced phase purity

Yamamoto

Jiang

Kametani

et al. 2011

Supercond. Sci. Technol.

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We prepared polycrystalline SmFeAsO 1-x F x (Sm1111) bulk samples by sintering and hot isostatic pressing (HIP) in order to study the effects of phase purity and relative density on the intergranular current density. Sintered and HIPped Sm1111 samples are denser with fewer impurity phases, such as SmOF and the grain boundary wetting phase, FeAs. We found quite complex magnetization behavior due to variations of both the inter and intragranular current densities. Removing porosity and reducing second phase content enhanced the intergranular current density, but HIPping reduced T c and the intragranular current density, due to loss of fluorine and reduction of T c . We believe that the HIPped samples are amongst the purest polycrystalline 1111 samples yet made. However, their intergranular current densities are still small, providing further evidence that polycrystalline pnictides, like polycrystalline cuprates, are intrinsically granular. 2 IntroductionThe discovery of superconductivity in LaFeAs(O,F) with critical temperature T c of 26 K was announced by Hosono et al. 1 in February 2008. This event prompted an army of physicists, chemists and material scientists to study these materials and shortly thereafter many other Fe-based superconductors were discovered that are now grouped into 4 families, which are generally referred to as "1111" for REFeAsO, "122" for AEFe 2 As 2 , 2 "111" for LiFeAs 3 and "11" for Fe(Te,Se) 4 where RE denotes rare earth and AE denotes alkali earth. The critical temperatures, in the optimally doped compounds, range from 19 K to 55 K and have very high upper critical fields approaching ~300 T for 1111 5 and ~100 T for 122 doped with potassium 6 or cobalt 7 . These favorable characteristics make it urgent to explore their potential for applications with the hope that practical conductors can be made with these Fe-based superconductors using simpler processes than are needed with high-temperature cuprate superconductors. 8 Actually these new Fe-based superconductors share several characteristics with cuprates including: layered structures, coexistence of different orderings, occurrence of superconductivity upon doping, short coherence length and unconventional pairing. In cuprates all these features have been shown to be unfavorable for applications. On the other hand, the available results show that both impurities 9,10 and grain boundaries 11,12 are less detrimental to the superconducting properties of these Fe-based superconductors than to the cuprates. Use of Fe-based superconductors in largescale applications would be greatly enhanced if polycrystalline samples were not intrinsically electromagnetically granular, as is the case for the cuprates. However, investigations of the critical current density (J c ) of 1111 polycrystalline samples have all shown significant evidence for granularity and low intergranular J c values. 11,13,14,15,16,17 In our previous study, evidence for two distinct scales of current flow was found in polycrystalline Sm-and Nd -1111 samples using magneto-optica...

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New Fe-based superconductors: properties relevant for applications

Cited by 278 publications

References 65 publications

Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors

Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors

High transport critical current densities in textured Fe-sheathed Sr1−xKxFe2As2+Sn superconducting tapes

Evidence for electromagnetic granularity in polycrystalline Sm1111 iron-pnictides with enhanced phase purity

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