Magneto-optical characterizations of FeTe0.5Se0.5thin films with critical current density over 1 MA cm−2

Sun, Yue; Tsuchiya, Yuji; Pyon, Sunseng; Tamegai, T.; Zhang, Cheng; Ozaki, Toshinori; Li, Qiang

doi:10.1088/0953-2048/28/1/015010

Cited by 12 publications

(11 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…All these data indicate that our crystals are highly pure. in the present case) [19], J c at 30 K under the self-field is evaluated as 0.33 MA/cm 2 .…”

Section: Resultsmentioning

confidence: 97%

“…Next we performed magneto-optical (MO) imaging of a CaKFe 4 As 4 single crystal to evaluate its homogeneity and the value of in-plane J c . in the present case) [19], J c at 30 K under the self-field is evaluated as 0.33 MA/cm 2 .…”

Section: Resultsmentioning

confidence: 97%

“…At lower temperatures, however, the magnetic induction profiles are saturated around 700 G because of large J c and the saturation of the magnetization of the indicator film. From the value of the trapped field, J c can be roughly evaluated[19]. At 30 K, magnetic induction B of 580 G is trapped.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Large and significantly anisotropic critical current density induced by planar defects in CaKFe4As4 single crystals

et al. 2019

Self Cite

View full text Add to dashboard Cite

Three independent components of critical current density, one for the H//c axis and the other two for the H//ab plane, have been studied in CaKFe 4 As 4 single crystals. When the magnetic field is applied along the c axis, we observed fish-tail-like peaks in the M-H hysteresis loop, and the magnetization at higher temperatures exceeds that at lower temperatures at high fields. When the field is applied parallel to the ab plane, a dip structure is observed in the M-H hysteresis loop near the self-field. In addition, for the H//ab plane, we succeeded in separately evaluating the large and significantly anisotropic in-plane and out-of-plane J c . Transmission electron microscopy revealed the presence of planar defects parallel to the ab plane in CaKFe 4 As 4 , which have not been observed in any other iron-based superconductors. We discuss the possible relationship between the anomalous J c behavior and the planar defects. anisotropy parameter  = H c2 ab /H c2 c is evaluated from the temperature dependence of H c2 (T). The temperature dependences of H c2 are summarized in Fig. 2(c). The definitions of T c onset and T c end are shown in Fig. 2(a). Estimated  at T ~ 34 K is 2.2. This value is consistent with the former report by Meier et al. [12], and similar to that of 122-type compounds of (Ba,K)Fe 2 As 2 with  ~ 2-3 near T c [4]. Next we performed magneto-optical (MO) imaging of a CaKFe 4 As 4 single crystal to evaluate its homogeneity and the value of in-plane J c . Figure 3(c) shows an optical micrograph of the crystal, which shows a smooth surface with no visible cracks. Figures 3(a) and 3(b) display MO images of the CaKFe 4 As 4 single crystal in the remanent state at (a) 5 K and (b) 35 K, respectively, after cycling the field up to 1.6 kOe for 0.2 s. At 5 K, the magnetic field does not fully penetrate the sample because of large J c and limitation of the value of the applied field. On the other hand, the magnetic field fully penetrates the sample at 35 K, and the MO image shows the critical state field profile expected for a uniform thin-plate superconductor with clear current discontinuity lines (d-lines).Local magnetic induction profiles at different temperatures taken along the dotted line in Fig. 3(a) are shown in Fig. 3(d). Magnetic induction profiles at higher temperatures of 30 and 35 K show roof-top patterns, indicating that the large and homogeneous current flows throughout the sample. At lower temperatures, however, the magnetic induction profiles are saturated around 700 G because of large J c and the saturation of the magnetization of the indicator film. From the value of the trapped field, J c can be roughly evaluated [19]. At 30 K, magnetic induction B of 580 G is trapped. Using t l l c (0<<1) = 1 H J c2 J c3 H t l l c (0<<1) = 2 J c2 J c3 (c) (d)

show abstract

“…All these data indicate that our crystals are highly pure. in the present case) [19], J c at 30 K under the self-field is evaluated as 0.33 MA/cm 2 .…”

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 97%

See 1 more Smart Citation

Large and significantly anisotropic critical current density induced by planar defects in CaKFe4As4 single crystals

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…From the value of the trapped field, J c can be roughly evaluated [24]. At 20 K, trapped magnetic induction B is 581 G. Using the approximate formula between B and J c for a thin superconductor with a thickness t, J c ∼ B /(t * ), with t = 9 m (β is a parameter determined by the sample dimensions and he distance between the sample surface and the garnet film, and β ~ 3.3 in the present case) [24], [25], or CaKFe 4 As 4 [26,27], and values of  ab at room temperature are very similar. In general, an electrical resistivity is inversely proportional to the mean free path of electrons l in metals.…”

Section: Resultsmentioning

confidence: 99%

Anisotropic physical properties and large critical current density in KCa2Fe4As4F2 single crystal

Pyon

Kobayashi

et al. 2020

Phys. Rev. Materials

Self Cite

View full text Add to dashboard Cite

We present a systematic study of electrical resistivity, Hall coefficient, magneto-optical imaging, magnetization, and STEM analyses of KCa 2 Fe 4 As 4 F 2 single crystals. Sharp diamagnetic transition and magneto-optical imaging reveal homogeneity of single crystal and prominent Bean-like penetrations of vortices. Large anisotropy of electrical resistivity, with  c / ab > 100, and semiconductor-like  c suggest that the electronic state is quasi two-dimensional. Hall effect measurements indicate that KCa 2 Fe 4 As 4 F 2 is a multiband system with holes as main carriers.Magnetization measurements reveal significantly larger J c compared with that in other iron-based superconductors with different values of J c depending on the direction of magnetic field. Origin of these J c characteristics is discussed based on microstructural observations using STEM. In addition, further enhancement of J c in KCa 2 Fe 4 As 4 F 2 for future application is demonstrated in terms of heavy-ion irradiation.

show abstract

“…[9][10][11] High self-field J c above 1 MA/cm 2 was also reported in iron chalcogenide films. 12,13 Most recently, a high field isotropic J c has been observed in FeSe 0.5 Te 0.5 thin films grown on CaF 2 substrates with a self-field J c over 2 MA/cm 2 at 5 K. 14 There are some concerns for the practical application of the iron-based superconductors. For example, the toxic element As in the most studied system, iron pnictides, is one of them, although the superconducting iron pnictides have a relatively higher T c and J c among iron-based superconductors.…”

mentioning

confidence: 99%

Doubling the critical current density in superconducting FeSe0.5Te0.5 thin films by low temperature oxygen annealing

Zhang

2016

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

Iron-chalcogenide superconducting thin films and coated conductors are attractive for potential high field applications at liquid helium temperature for their high critical current densities J c , low anisotropies, and relatively strong grain couplings. Embedding flux pinning defects is a general approach to increase the in-field performance of superconductors. However, many effective pinning defects can adversely affect the zero field or self-field J c , particularly in cuprate high temperature superconductors. Here, we report doubling of the self-field J c in FeSe 0.5 Te 0.5 films by low temperature oxygen annealing, reaching ~3 MA/cm 2 . In-field performance is also dramatically enhanced. Our results demonstrate that low temperature oxygen annealing is a simple and cost-efficient post-treatment technique which can greatly help to accelerate the potential high field applications of the iron-based superconductors.

show abstract

Magneto-optical characterizations of FeTe_0.5Se_0.5thin films with critical current density over 1 MA cm⁻²

Cited by 12 publications

References 31 publications

Large and significantly anisotropic critical current density induced by planar defects in CaKFe4As4 single crystals

Large and significantly anisotropic critical current density induced by planar defects in CaKFe4As4 single crystals

Anisotropic physical properties and large critical current density in KCa2Fe4As4F2 single crystal

Doubling the critical current density in superconducting FeSe0.5Te0.5 thin films by low temperature oxygen annealing

Contact Info

Product

Resources

About