Grain Boundaries in Fe-Based Superconductors

Hänisch, Jens; Iida, K.

doi:10.1007/978-3-030-23303-7_10

Cited by 4 publications

(2 citation statements)

References 114 publications

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“…Additionally, excellent review articles concerning bicrystals and GBs in cuprates have already been published [3,5,6], however, only a few on GB issues for FBS have been published (e.g. [7,8]).…”

Section: Introductionmentioning

confidence: 99%

Grain boundary characteristics of Fe-based superconductors

Iida

Hänisch

Yamamoto

2020

Supercond. Sci. Technol.

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the distance between strained regions is smaller or only slightly larger than the value of ξ within the GB plane, the superconducting order parameter is depressed at the GB and, hence, the super-current flow is impeded. Additionally, bending of the electronic bands at GBs deplete the charge carrier density 3 , which seriously decreases the superconducting transition temperature T c . Hence, to achieve large J c for cuprates, the crystallites should not only be aligned out-of-plane because J c is anisotropic but also be aligned in-plane within the misorientation angle θ GB , where the distance between strained regions is larger than ξ ab (ξ ab : in-plane coherence length) is satisfied. On the other hand, for LTS and MgB 2 with large coherence length (e.g. 5∼6 nm) and s-wave symmetry (for MgB 2 anisotropic swave), GBs are able to pin vortices in the mixed state, and especially also GBs with rather large angles. Therefore, increasing the GB densities by reducing the grain size usually leads to improved in-field J c properties.As stated above, the symmetry of superconducting order parameter and the coherence length mainly govern the J c characteristics at GBs for a given superconductor. Hence, for both LTS and HTS, understanding the nature of GB characteristics in combination with modifying the processing conditions, so-called GB engineering, is of great importance for reducing and/or controlling the defect density to tune the superconducting properties.The Fe-based superconductors (FBS) have similar physical properties as the cuprates, for instance a short coherence length due to the small carrier concentration and a low Fermi velocity 4 . Hence, FBS also seem to share the same GB issues as the cuprates. However, J c across GBs in FBS is not as severely reduced due to several features, which is reviewed in this article. Many reviews of the synthesis of FBS in the form of bulk samples and thin films, and of their physical properties have been published to date. Additionally, excellent review articles concerning bicrystals and GBs in cuprates have already been published 3,5,6 , however, only a few on GB issues for FBS have been published (e.g. 7 and 8). Grant Number 16H04646 as well as JST CREST Grant Number JPMJCR18J4. REFERENCES 1 Tomimoto K, Terasaki I, Rykov A I, Miura T and Tajima S, 1999 Phys. Rev. B 60 114 2 Tsuei C C and Kirtley J R 2000 Rev. Mod. Phys. 72 969 3 Hilgenkamp H and Mannhart J 2002 Rev. Mod. Phys. 74 485

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Section: Introductionmentioning

confidence: 99%

Grain boundary characteristics of Fe-based superconductors

Iida

Hänisch

Yamamoto

2020

Supercond. Sci. Technol.

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“…This paper concentrates on the temperature dependent anisotropy of B c2 , the pseudoisotropy towards zero temperature, and the in-plane and out-of-plane coherence lengths. There is also a great deal of interest in critical current densities in magnetic fields and the underlying pinning mechanisms [5,42,[45][46][47][48][49] mainly with respect to large-scale applications. Here, we measured the critical current density in dependence on temperature and magnetic field and its anisotropy.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic field dependence of the electronic transport in superconducting FeSe thin films

Schneider

Zaitsev

Fuchs

et al. 2020

Supercond. Sci. Technol.

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Electronic transport measurements were carried out on c-axis oriented epitaxial FeSe thin films in static magnetic fields up to 14 T parallel to the crystallographic c-axis and parallel to the ab-plane. The temperature dependence of the upper critical fields B c c2 and B ab c2 was determined from the field dependence of the resistivity. While B c c2 was orbitally limited, the larger B ab c2 was paramagnetically limited. The anisotropy γ B was decreasing with decreasing temperature and revealed a pseudoisotropic behaviour towards zero temperature. This temperature dependence is indicative of the multiband character of FeSe. From measurements of the temperature-and field-dependent critical current densities the effective depinning or irreversibility field B * c2 was obtained, and its angular dependence yielded the effective mass anisotropy γ m . The temperature dependence of γ m , which was different from that of γ B , can be considered as another signature of multiband FeSe.

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Approaching the ultimate superconducting properties of (Ba,K)Fe2As2 by naturally formed low-angle grain boundary networks

et al. 2021

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The most effective way to enhance the dissipation-free supercurrent in the presence of a magnetic field for type II superconductors is to introduce defects that act as artificial pinning centers (APCs) for vortices. For instance, the in-field critical current density of doped BaFe2As2 (Ba122), one of the most technologically important Fe-based superconductors, has been improved over the last decade by APCs created by ion irradiation. The technique of ion irradiation has been commonly implemented to determine the ultimate superconducting properties. However, this method is rather complicated and expensive. Here, we report a surprisingly high critical current density and strong pinning efficiency close to the crystallographic c-axis for a K-doped Ba122 epitaxial thin film without APCs, achieving performance comparable to ion-irradiated K-doped Ba122 single crystals. Microstructural analysis reveals that the film is composed of columnar grains with widths of approximately 30–60 nm. The grains are rotated around the b- (or a-) axis by 1.5° and around the c-axis by −1°, resulting in the formation of low-angle grain boundary networks. This study demonstrates that the upper limit of in-field properties reached in ion-irradiated K-doped Ba122 is achievable by grain boundary engineering, which is a simple and industrially scalable manner.

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Grain Boundaries in Fe-Based Superconductors

Cited by 4 publications

References 114 publications

Grain boundary characteristics of Fe-based superconductors

Grain boundary characteristics of Fe-based superconductors

Anisotropic field dependence of the electronic transport in superconducting FeSe thin films

Approaching the ultimate superconducting properties of (Ba,K)Fe2As2 by naturally formed low-angle grain boundary networks

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