Anisotropy in Superconductivity and Magnetism of PrFeAsO1−δ Single Crystal

Kubota, D.; Ishida, Toshimasa; Ishikado, M.; Shamoto, S.; Eisaki, H.; Kitô, Hijiri; Iyo, A.

doi:10.1007/s10948-010-0714-z

Cited by 2 publications

(2 citation statements)

References 8 publications

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“…However, the reliable measurement of the lower critical field is a difficult task, in particular when strong vortex pinning is present as in the case of Fe-arsenides. We also point out that to date the reported values of anisotropy parameter strongly vary [31,32,33,34] Here we review our microwave surface impedance Z s measurements in single crystals of electrondoped PrFeAsO 1−y (y ∼ 0.1) [35] and hole-doped Ba 1−x K x Fe 2 As 2 (x ≈ 0.55) [36]. By using a sensitive superconducting cavity resonator, we can measure both real and imaginary parts of Z s pricesely in tiny single crystals, from which we can extract the in-plane penetration depth λ ab (T ) as well as quasiparticle conductivity σ 1 (T ) that yields information on the quasiparticle dynamics.…”

Section: Introductionmentioning

confidence: 82%

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Shibauchi

Hashimoto

Okazaki

et al. 2009

Physica C: Superconductivity

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In this article, we review our recent studies of microwave penetration depth, lower critical fields, and quasiparticle conductivity in the superconducting state of Fe-arsenide superconductors. Highsensitivity microwave surface impedance measurements of the in-plane penetration depth λ ab in single crystals of electron-doped PrFeAsO1−y (y ∼ 0.1) and hole-doped Ba1−xKxFe2As2 (x ≈ 0.55) are presented. In clean crystals of Ba1−xKxFe2As2, as well as in PrFeAsO1−y crystals, the penetration depth shows flat temperature dependence at low temperatures, indicating that the superconducting gap opens all over the Fermi surface. The temperature dependence of superfluid density λ 2 ab (0)/λ 2 ab (T ) in both systems is most consistent with the existence of two different gaps. In Ba1−xKxFe2As2, we find that the superfluid density is sensitive to degrees of disorder inherent in the crystals, implying unconventional impurity effect. We also determine the lower critical field Hc1 in PrFeAsO1−y by using an array of micro-Hall probes. The temperature dependence of Hc1 saturates at low temperatures, fully consistent with the superfluid density determined by microwave measurements. The anisotropy of Hc1 has a weak temperature dependence with smaller values than the anisotropy of upper critical fields at low temperatures, which further supports the multi-gap superconductivity in Fe-arsenide systems. The quasiparticle conductivity shows an enhancement in the superconducting state, which suggests the reduction of quasiparticle scattering rate due to the gap formation below Tc. From these results, we discuss the structure of the superconducting gap in these Fe-arsenides, in comparison with the high-Tc cuprate superconductors.

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Section: Introductionmentioning

confidence: 82%

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Shibauchi

Hashimoto

Okazaki

et al. 2009

Physica C: Superconductivity

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“…cuprates and MgB 2 ) a detailed knowledge of c in the oxypnictides is required. Various attempts were made to estimate anisotropy in the oxypnictide superconductors [31][32][33][34][35][36][37][38][39][40][41][42], leading to a wide range of results. Nevertheless, from both experimental and theoretical sides there is clear evidence that superconductivity in the pnictides involves more than one-band [31][32][33][43][44][45][46][47][48] and therefore it is expected that anisotropy is temperature dependent.…”

Section: Introductionmentioning

confidence: 99%

Single crystals of LnFeAsO1−xFx (Ln=La, Pr, Nd, Sm, Gd) and Ba1−xRbxFe2As2: Growth, structure and superconducting properties

Karpiński¹,

Zhigadlo²,

Katrych³

et al. 2009

Physica C: Superconductivity

135

141

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a b s t r a c tA review of our investigations on single crystals of LnFeAsO 1Àx F x (Ln = La, Pr, Nd, Sm, Gd) and Ba 1Àx -Rb x Fe 2 As 2 is presented. A high-pressure technique has been applied for the growth of LnFeAsO 1Àx F x crystals, while Ba 1Àx Rb x Fe 2 As 2 crystals were grown using a quartz ampoule method. Single crystals were used for electrical transport, structure, magnetic torque and spectroscopic studies. Investigations of the crystal structure confirmed high structural perfection and show incomplete occupation of the (O, F) position in superconducting LnFeAsO 1Àx F x crystals. Resistivity measurements on LnFeAsO 1Àx F x crystals show a significant broadening of the transition in high magnetic fields, whereas the resistive transition in Ba 1Àx Rb x Fe 2 As 2 simply shifts to lower temperature. The critical current density for both compounds is relatively high and exceeds 2 Â 10 9 A/m 2 at 15 K in 7 T. The anisotropy of magnetic penetration depth, measured on LnFeAsO 1Àx F x crystals by torque magnetometry is temperature dependent and apparently larger than the anisotropy of the upper critical field. Ba 1Àx Rb x Fe 2 As 2 crystals are electronically significantly less anisotropic. Point-Contact Andreev-Reflection spectroscopy indicates the existence of two energy gaps in LnFeAsO 1Àx F x . Scanning Tunneling Spectroscopy reveals in addition to a superconducting gap, also some feature at high energy ($20 meV).

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Anisotropy in Superconductivity and Magnetism of PrFeAsO1−δ Single Crystal

Cited by 2 publications

References 8 publications

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Single crystals of LnFeAsO1−xFx (Ln=La, Pr, Nd, Sm, Gd) and Ba1−xRbxFe2As2: Growth, structure and superconducting properties

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