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Journal Articles

Effects of high-pressure annealing on critical current density in 122 type iron pnictide wires

Pyon, S.*; Tsuchiya, Yuji*; Inoue, Hiroshi*; Koizumi, Norikiyo; Kajitani, Hideki; Tamegai, Tsuyoshi*

Physica C, 504, p.69 - 72, 2014/09

 Times Cited Count:3 Percentile:17.38(Physics, Applied)

no abstracts in English

Journal Articles

Comparison of $$J$$c characteristics in PIT wires based on BaFe$$_{2}$$As$$_{2}$$ with different substitutions

Tamegai, Tsuyoshi*; Pyon, S.*; Ding, Q. P.*; Inoue, Hiroshi*; Kobayashi, Hiroki*; Tsuchiya, Yuji*; Sun, Y.*; Kajitani, Hideki; Koizumi, Norikiyo

Journal of Physics; Conference Series, 507(2), p.022041_1 - 022041_4, 2014/05

 Times Cited Count:3 Percentile:80.74

The author studied the effect of chemical compound for superconducting performance ($$J$$c) of iron-based superconductors. As a result, it was revealed that BaFe$$_{2}$$As$$_{2}$$ showed high Jc. And more, BaFe$$_{2}$$As$$_{2}$$ showed higer $$J$$c such as 32,000A/cm$$^{2}$$ (4.2K) by being applied of 120 MPa of hot isostatic pressure (HIP). Thus, higher $$J$$c performance could be achieved.

Journal Articles

Enhancement of critical current densities in (Ba,K)Fe$$_{2}$$As$$_{2}$$ by 320 MeV Au irradiation in single crystals and by high-pressure sintering in powder-in-tube wires

Pyon, S.*; Taen, Toshihiro*; Otake, Fumiaki*; Tsuchiya, Yuji*; Inoue, Hiroshi*; Akiyama, Hiroki*; Kajitani, Hideki; Koizumi, Norikiyo; Okayasu, Satoru; Tamegai, Tsuyoshi*

Applied Physics Express, 6(12), p.123101_1 - 123101_4, 2013/12

 Times Cited Count:19 Percentile:67.04(Physics, Applied)

We demonstrate a large enhancement of critical current density ($$J$$$$_{rm c}$$) up to 1.0 $$times$$ 10$$^{7}$$ A/cm$$^{2}$$ at 5 K under self-field in (Ba,K)Fe$$_{2}$$As$$_{2}$$ single crystals by irradiating 320 MeV Au ions. With the very promising potential of this material in mind, we have fabricated a (Ba,K)Fe$$_{2}$$As$$_{2}$$ superconducting wire through a powder-in-tube method combined with the hot isostatic pressing technique, whose effectiveness has been proven in industrial Bi2223 tapes. The Jc in the wire at 4.2 K has reached 37 kA/cm$$^{2}$$ under self-field and 3.0 kA/cm$$^{2}$$ at 90 kOe. Magneto-optical imaging of the wire confirmed the large intergranular Jc in the wire core.

Journal Articles

Effects of irradiation-particle energy on critical current density in Co-doped BaFe$$_{2}$$As$$_{2}$$

Taen, Toshihiro*; Yagyuda, Hidenori*; Nakajima, Yasuyuki*; Tamegai, Tsuyoshi*; Okayasu, Satoru; Kitamura, Hisashi*; Murakami, Takeshi*; Laviano, F.*; Ghigo, G.*

Physica C, 484, p.62 - 65, 2013/01

 Times Cited Count:8 Percentile:41.17(Physics, Applied)

We report effects of particle energy on physical properties of Co-doped BaFe$$_{2}$$As$$_{2}$$ in the case of Xe and Au irradiations. The irradiation-induced suppression of $$T$$$$_{rm c}$$ is found to be related with several factors, such as defect structures and the thickness of the crystal. Heavy-ion irradiation induces enhancement of critical current density $$J$$$$_{rm c}$$, and a weak dip in the hysteresis loop. The fish-tail effect is completely suppressed by a modest density of defects. The enhancement of $$J$$$$_{rm c}$$ is closely related to the defect structure. Namely, splayed structure in columnar defects, inevitably introduced at lower energies, results in a strong enhancement of $$J$$$$_{rm c}$$ by forced entanglement of vortices.

Journal Articles

Reports for the 10th International Conference M2S

Tamegai, Tsuyoshi*; Adachi, Tadashi*; Nagai, Yuki

Kotai Butsuri, 47(12), p.779 - 784, 2012/12

no abstracts in English

Journal Articles

Effects of particle irradiations on vortex states in iron-based superconductors

Tamegai, Tsuyoshi*; Taen, Toshihiro*; Yagyuda, Hidenori*; Tsuchiya, Yuji*; Mohan, S.*; Taniguchi, Tomotaka*; Nakajima, Yasuyuki*; Okayasu, Satoru; Sasase, Masato*; Kitamura, Hisashi*; et al.

Superconductor Science and Technology, 25(8), p.084008_1 - 084008_14, 2012/08

 Times Cited Count:77 Percentile:93.85(Physics, Applied)

Various kinds of energetic particles are irradiated into iron-based superconductors, and their effects on the critical current density $$J$$$$_{rm c}$$ and vortex dynamics have been systematically studied. It is found that $$J$$$$_{rm c}$$ is enhanced and vortex dynamics is strongly suppressed by energetic particles having a sufficient energy deposition rate, similar to the case of high temperature cuprate superconductors. The enhancement of $$J$$$$_{rm c}$$, in general, persists up to much higher irradiation doses than in cuprates. However, details of the effect of irradiation depend on the kind of ion species and their energies. Even with the same ions and energies, the effect is not universal for different kinds of iron-based superconductors. The correlated nature of defects created by heavy-ion irradiation is confirmed by the angular dependence of irreversible magnetization.

Journal Articles

Low-field anomaly of vortex dynamics in iron-pnictide superconductors

Tamegai, Tsuyoshi*; Taen, Toshihiro*; Yagyuda, Hidenori*; Nakajima, Yasuyuki*; Okayasu, Satoru; Sasase, Masato*; Kitamura, Hisashi*; Murakami, Takeshi*; Kambara, Tadashi*; Kanai, Yasuyuki*

Physica C, 471, p.777 - 780, 2011/00

 Times Cited Count:6 Percentile:31.79(Physics, Applied)

Magnetic relaxations in Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$ before and after swift particle irradiations are measured. The normalized relaxation rate S shows a clear suppression in a pristine sample at low fields below the self-field. Heavy-ion irradiations suppress these anomalies considerably, although there still remain weak features depending on ion species and/or energies. In a proton irradiated sample, the low-field anomaly of S survives although it is smeared compared with that in a pristine sample. All these results indicate that the low-field anomaly of S is suppressed by defects, and correlated defects have stronger effects.

Journal Articles

Effects of heavy-ion irradiation on the vortex state in Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$

Tamegai, Tsuyoshi*; Tsuchiya, Yuji*; Taen, Toshihiro*; Nakajima, Yasuyuki*; Okayasu, Satoru; Sasase, Masato*

Physica C, 470(Suppl.1), p.S360 - S362, 2010/12

 Times Cited Count:1 Percentile:7.06(Physics, Applied)

We report effects of heavy-ion irradiation in Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$ single crystals. The columnar defects with about 40% of the irradiation dose are confirmed by transmission electron microscopy. Magneto-optical imaging and bulk magnetization measurements reveal strong enhancement of the critical current density in the irradiated region. The vortex creep rate is also strongly suppressed by the columnar defects. Effects of heavy-ion irradiation into Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$ and cuprate superconductors are compared.

Journal Articles

Critical current densities and flux creep rate in Co-doped BaFe$$_{2}$$As$$_{2}$$ with columnar defects introduced by heavy-Ion irradiation

Nakajima, Yasuyuki*; Tsuchiya, Yuji*; Taen, Toshihiro*; Yagyuda, Hidenori*; Tamegai, Tsuyoshi*; Okayasu, Satoru; Sasase, Masato*; Kitamura, Hisashi*; Murakami, Takeshi*

Physica C, 470(20), p.1103 - 1105, 2010/11

 Times Cited Count:3 Percentile:18.65(Physics, Applied)

We report the formation of columnar defects in Co-doped BaFe$$_{2}$$As$$_{2}$$ single crystals with different heavy ion irradiations. The formation of columnar defects by 200 MeV Au ion irradiation is confirmed by transmission electron microscopy and their density is about 40% of the irradiation dose. Magneto-optical imaging and bulk magnetization measurements reveal that the critical current density $$J$$$$_{rm c}$$ is enhanced in the 200 MeV Au and 800 MeV Xe ion irradiated samples while $$J$$$$_{rm c}$$ is unchanged in the 200 MeV Ni ion irradiated sample. We also find that vortex creep rates are strongly suppressed by the columnar defects. We compare the effect of heavy-ion irradiation into Co-doped BaFe$$_{2}$$As$$_{2}$$ and cuprate superconductors.

Journal Articles

Critical current densities and vortex dynamics in Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$ single crystals

Tamegai, Tsuyoshi*; Taen, Toshihiro*; Tsuchiya, Yuji*; Nakajima, Yasuyuki*; Okayasu, Satoru; Sasase, Masato*

Journal of Superconductivity and Novel Magnetism, 23(5), p.605 - 608, 2010/07

 Times Cited Count:0 Percentile:0(Physics, Applied)

Superconducting properties are evaluated for high-quality single crystals of Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$ in a wide range of doping levels. The critical current density, $$J$$$$_{rm c}$$, in an optimally-doped crystal (Tc $$sim$$ 24 K) shows a fishtail effect with its value over 10$$^{5}$$ A/cm$$^{2}$$ even at 5 T below 10 K. Magneto-optical imaging has clarified rather homogeneous supercurrent flow in the crystal, in spite of a large amount of impurities. In the heavy-ion irradiated sample, the presence of columnar defects are confirmed and $$J$$$$_{rm c}$$ has been enhanced by a factor of five at low temperatures, reaching 6 $$times$$ 10$$^{6}$$ A/cm$$^{2}$$ at 2 K under zero field. Flux creep rate in the heavy-ion irradiated sample has been reduced in accordance with the enhancement of $$J$$$$_{rm c}$$.

Journal Articles

Phonon density of states in Sr$$_{2}$$FeCoO$$_{6-delta}$$ and SrBaFeCoO$$_{6-delta}$$; Effects induced by magnetic order and transport coherence

Rykov, A. I.*; Nomura, Kiyoshi*; Sawada, Tsuguo*; Mitsui, Takaya; Seto, Makoto*; Tamegai, Tsuyoshi*; Tokunaga, Masashi*

Physical Review B, 68(22), p.224401_1 - 224401_7, 2003/12

 Times Cited Count:8 Percentile:44.11(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Microwave properties perpendicular to the CuO$$_{2}$$ planes

*; *; Maeda, A.*; Tamegai, Tsuyoshi*; *; *; *; Asaoka, Hidehito; *

Physica C, 235-240, p.1819 - 1820, 1994/00

 Times Cited Count:2 Percentile:21.2(Physics, Applied)

no abstracts in English

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