Critical current density and vortex dynamics in pristine and proton-irradiated Ba0.6K0.4Fe2As2

Taen, Toshihiro; Ohtake, Fumiaki; Pyon, Sunseng; Tamegai, T.; Kitamura, Hisashi

doi:10.1088/0953-2048/28/8/085003

Cited by 61 publications

(73 citation statements)

References 54 publications

(111 reference statements)

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“…Ba 0.6 K 0.4 Fe 2 As 2 single crystals (T c ∼ 38 K) were synthesized by FeAs flux method [11,12,13], and Ba(Fe 0.93 Co 0.07 ) 2 As 2 single crystals (T c ∼ 24 K) were synthesized by FeAs/CoAs flux method [14]. The crystals were shaped into rectangular parallelepiped with length and width of approximately 500 µm and with thickness below half of the projected range of ions.…”

Section: Experimental Methodsmentioning

confidence: 99%

Anisotropy of critical current densities in Ba_1−xK _x Fe₂As₂ and Ba(Fe_1−xCo _x )₂As₂ with splayed columnar defects

Ito

Pyon

Kambara

et al. 2018

J. Phys.: Conf. Ser.

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Abstract. Effects of bimodal splayed columnar defects in Ba 1−xKxFe2As2 and Ba(Fe1−xCox)2As2 single crystals through 2.6 GeV U irradiation and 220 MeV Au irradiation are investigated. Magnetic field profiles measured by magneto-optical imaging clarified the presence of in-plane anisotropy of the critical current density (Jc) in 2.6 GeV U irradiated crystals, where Jc parallel to the splay plane is larger than that perpendicular to the splay plane. However, the in-plane anisotropy of Jc is absent in 220MeV Au irradiated crystals. Possible origin of this discrepancy is discussed based on the structure of introduced defects. IntroductionColumnar defects in type-II superconductors serve as artificial pinning centers, which lead to an enhancement of critical current density J c [1,2,3]. It has been proposed that a further enhancement of J c is possible by dispersing the direction of the columnar defects [4]. In such a system with splayed columnar defects, enhancement of J c has been confirmed in 1.08 GeV Au irradiated YBa 2 Cu 3 O 7−δ single crystals [5] and 2.6 GeV U irradiated Ba 1−x K x Fe 2 As 2 single crystals [6]. Due to the competing effects of suppression of vortex motion by unequal lengths of vortex segments between splayed columnar defects and detrimental effect of misalignment of vortices, the optimal splay angles were found to be ≈ ±5 • in both of the above systems.However, since these results were obtained through magnetization measurements, the estimated J c is a weighted average of J c 's along two directions in the ab plane. Since directions parallel and perpendicular to the splay plane of columnar defects can be distinguished in a system with bimodal splayed columnar defects, J c parallel to the splay direction (J c∥ ) and J c perpendicular to the splay direction (J c⊥ ) can be different. Such an in-plane anisotropy of J c in systems with splayed columnar defects has been confirmed through resistivity measurements in 1 GeV Au irradiated YBa 2 Cu 3 O 7−δ [7] and 3.9 GeV Au irradiated YBa 2 Cu 3 O 7−δ [8], where Ohmic dissipation was higher when the current is passed in the direction perpendicular to the

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Section: Experimental Methodsmentioning

confidence: 99%

Anisotropy of critical current densities in Ba_1−xK _x Fe₂As₂ and Ba(Fe_1−xCo _x )₂As₂ with splayed columnar defects

Ito

Pyon

Kambara

et al. 2018

J. Phys.: Conf. Ser.

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“…So far, some groups reported the existence of the SMP effect in optimally-doped K-Ba122 [24,31] whereas other groups reported its absence [44,56]. The apparent discrepancy likely comes from a slight difference in the effective x.…”

Section: Magnetization Hysteresis Loopsmentioning

confidence: 98%

Doping-dependent critical current properties in K, Co, and P-doped BaFe2As2 single crystals

et al. 2017

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* Both authors contributed equally to this work.In order to establish the doping dependence of the critical current properties in the iron-based superconductors, the in-plane critical current density (Jc) of BaFe2As2-based superconductors, Ba1-xKxFe2As2 (K-Ba122), Ba(Fe1-xCox)2As2 (Co-Ba122), and BaFe2(As1-xPx)2 (P-Ba122) in a wide range of doping concentration (x) was investigated by means of magnetization hysteresis loop (MHL) measurements on single crystal samples. Depending on the dopant elements and their concentration, Jc exhibits a variety of magneticfield (H)-and temperature (T)-dependences. (1) In the case of K-Ba122, the MHL of the under-doped samples (x ≤ 0.33) exhibits the second magnetization peak (SMP), which sustains high Jc at high H and high T, exceeding 10 5 A/cm 2 at T = 25 K and µ0H = 6 T for x = 0.30. On the other hand, the SMP is missing in the optimally-(x ~ 0.36-0.40) and over-doped (x ~ 0.50) samples, and consequently Jc rapidly decreases by more than one order of magnitude, although the change in Tc is within a few K. (2) For Co-Ba122, the SMP is always present over the entire superconducting (SC) dome from the under-(x ~ 0.05) to the over-doped (x ~ 0.12) region. However, the magnitude of Jc significantly changes with x, exhibiting a sharp maximum at x ~ 0.057, which is a slightly under-doped composition among Co-Ba122. (3) For P-Ba122, the highest Jc is attained at x = 0.30 corresponding to the highest Tc composition. For the over-doped samples, the MHL is characterized by a SMP located close to the irreversibility field Hirr. Common to the three doping variations, Jc becomes highest at the under-doping side of the SC dome near the phase boundary between the SC phase and the antiferromagnetic/orthorhombic (AFO) phase. Also, the peak appears in a narrow range of doping, distinct from the Tc dome with broad maximum. These similarities in the three cases indicate that the observed doping dependence of Jc is intrinsic to the BaFe2As2-based superconductors. The scaling analysis of the normalized pinning force density fp as a function of the reduced magnetic field h = H/Hirr (Hirr: irreversibility field) shows that the peak in the pinning force position (hmax) depends on x, indicating a change in pinning with x. On the other hand, high-Jc samples always attain similar hmax values of 0.40-0.45 for all the dopants, which may suggest that a common pinning source causes the highest Jc. A quantitative analysis of the Tdependent Jc indicates that the two pinning mechanisms, namely, the spatial variations in Tc (referred to as Tc pinning) and the fluctuations in the mean free path (l pinning), are enhanced for the under-doped samples, which results in the enhancement of Jc. Possible origins for the different pinning mechanism are discussed in connection with the x-dependence of Tc, the residual resistivity, AFO domain boundaries, and a possible quantum critical point.

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“…Single crystals of (Ba,K)Fe 2 As 2 also have achieved high J c over 1x10 6 A/cm 2 [15][16][17]. The fact that these values are almost the same level as commercially used NbTi or Nb 3 Sn wires makes IBSs very promising for high-field applications [18].…”

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confidence: 96%

Enhancement of critical current densities in (Ba,K)Fe₂As₂wires and tapes using HIP technique

Pyon

Suwa

Park

et al. 2016

Supercond. Sci. Technol.

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Abstract(Ba,K)Fe 2 As 2 superconducting wires and tapes are fabricated by using hot isostatic pressing (HIP) technique, and their superconducting properties are studied. In the HIP round wire, transport critical current density (J c ) at 4.2 K has achieved record-high value of 175 kA/cm 2 at zero field, and exceeds 20 kA/cm 2 even at 100 kOe. Improvement of polycrystalline powder synthesis may play a key role for the enhancement of J c . In the HIP tape, even larger transport J c of 380 kA/cm 2 is realized at zero field. Based on magnetization and magneto-optical measurements, possible further enhancement of J c is discussed.

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Critical current density and vortex dynamics in pristine and proton-irradiated Ba_0.6K_0.4Fe₂As₂

Cited by 61 publications

References 54 publications

Anisotropy of critical current densities in Ba_1−xK _x Fe₂As₂ and Ba(Fe_1−xCo _x )₂As₂ with splayed columnar defects

Anisotropy of critical current densities in Ba_1−xK _x Fe₂As₂ and Ba(Fe_1−xCo _x )₂As₂ with splayed columnar defects

Doping-dependent critical current properties in K, Co, and P-doped BaFe2As2 single crystals

Enhancement of critical current densities in (Ba,K)Fe₂As₂wires and tapes using HIP technique

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Critical current density and vortex dynamics in pristine and proton-irradiated Ba0.6K0.4Fe2As2

Cited by 61 publications

References 54 publications

Anisotropy of critical current densities in Ba1−x K x Fe2As2 and Ba(Fe1−x Co x )2As2 with splayed columnar defects

Anisotropy of critical current densities in Ba1−x K x Fe2As2 and Ba(Fe1−x Co x )2As2 with splayed columnar defects

Doping-dependent critical current properties in K, Co, and P-doped BaFe2As2 single crystals

Enhancement of critical current densities in (Ba,K)Fe2As2wires and tapes using HIP technique

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About

Critical current density and vortex dynamics in pristine and proton-irradiated Ba_0.6K_0.4Fe₂As₂

Anisotropy of critical current densities in Ba_1−xK _x Fe₂As₂ and Ba(Fe_1−xCo _x )₂As₂ with splayed columnar defects

Anisotropy of critical current densities in Ba_1−xK _x Fe₂As₂ and Ba(Fe_1−xCo _x )₂As₂ with splayed columnar defects

Enhancement of critical current densities in (Ba,K)Fe₂As₂wires and tapes using HIP technique