Recent progress on compositional nanostripes of REBa2Cu3O7−δ(RE = Sm,Eu,Gd) superconductors

Hu, Anming; Koblischka, Michael Rudolf; Yao, Xingyu; Zhou, Hao; Winter, M.; Hartmann, Uwe; Murakami, Masato

doi:10.1088/0953-2048/19/7/s31

Cited by 10 publications

(9 citation statements)

References 24 publications

(36 reference statements)

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“…3 (c,d) indicate that the step height continuously varies from about 2 nm to less than 1 nm. It was proposed [7] that the criss-cross structure originates from crossing annular stripes of a type similar to those shown in Figs. 3 (c,d).…”

Section: Resultsmentioning

confidence: 68%

“…by means of irradiation [5], it is essential for applications to create these defects intrinsically during the necessary sample processing steps. Recently, it was shown that by using appropriate melt-growth processes, bulk high-T c samples were grown which intrinsically include periodic nanometre-sized variations in their chemical composition throughout the whole sample volume [6,7]. These composition modulations are assumed to provide effective flux pinning centres by providing a δT c -type pinning, which is most effective in large applied magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

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Nanoscale flux pinning sites in high‐ T _c superconductors

Koblischka

Winter

et al. 2005

phys. stat. sol. (c)

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PACS 74.25.Qt, 74.40.+k, 74.81.Bd Ideal flux pining centres in high-T c superconductors should be of nanometre size as the coherence length, ξ, is so small. Therefore, the optimisation of high-T c superconductor samples concerning high critical current densities and high flux pinning has to take place in the nanometre range. An important goal of the current research is to find specific preparation strategies to create such ideal flux pining sites already during the sample processing. By means of AFM and STM measurements at ambient conditions, we have investigated the topographies of various samples of YBa 2 Cu 3 O x (YBCO), NdBa 2 Cu 3 O x (NdBCO), SmBa 2 Cu 3 O x (SmBCO), (Sm,Eu,Gd)Ba 2 Cu 3 O x (SEG) and (Nd,Eu,Gd)Ba 2 Cu 3 O x (NEG) high-T c superconductors. We find that the two systems with the highest critical current densities (NEG, SEG) and hence, the strongest flux pinning, exhibit microstructures on the nanometre scale which are remarkably different from those obtained in the YBCO system. The stripe-like growth structures observed in our topography measurements may be the key for the considerable improvements concerning the critical current densities especially at high magnetic fields and elevated operating temperature (77 K).

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Section: Resultsmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Nanoscale flux pinning sites in high‐ T _c superconductors

Koblischka

Winter

et al. 2005

phys. stat. sol. (c)

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“…These lamellae are due to composition variations of the (Nd, Eu, Gd)/Ba-ratio and (Sm, Eu, Gd)/Ba-ratio, respectively, around the 1:2 stoichiometric ratio as demonstrated in Refs. [14,15]. The lamellae have a width of about 20 − 50 nm, thus allowing the stripes to perform as excellent δT c -pinning sites.…”

Section: Resultsmentioning

confidence: 99%

Analysis of high‐ T _c superconductor compounds on the nanometre scale

Koblischka

Hartmann

2005

phys. stat. sol. (c)

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PACS 74.25.Qt, 74.40.+k, 74.81.Bd Due to the small coherence lengths of the high-T c compounds, effective pinning sites are defects or particles of nanometer size according to ξ 3 . Integral magnetic measurements of the magnetization as a function of temperature in large applied magnetic fields (up to 7 T) have revealed that practically all high-T c compounds exhibit spatial inhomogeneities, which can be caused by either oxygen deficiency (YBCO), solid solutions of Nd/Ba (NdBCO and light rare earth 123-type compounds), intergrowths (Bi-based superconductors) or chemical doping by pair-breaking dopants like Zn, Pr, etc. Such local variations of the superconducting properties should be visible in low-temperature scanning tunneling microscopy experiments, and their effects on flux pinning could be studied in a direct way. Various irradiation experiments by neutrons, protons, and heavy-ions have enabled the artificial introduction of effective pinning sites into the high-T c samples, thus creating many different observations in the integral magnetic data. Furthermore, several sub-structure formations are found in several multi-light rare earth 123-superconductor samples by means of AFM investigations, which may play an important role for the considerably improved critical current densities in these materials. From all these observations, we construct a pinning diagram explaining many features observed in high-T c samples.

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“…On the other hand, for the melt-textured samples or single crystals, local composition fluctuations, known as nanoclusters, were observed, consisting of the LRE 1+x Ba 2-x Cu 3 O y phase. The 10-50 nm dimension nanoclusters may work as highly effective pinning centres at higher magnetic fields, [7][8][9]. Oh et al [10] reported that higher critical current densities, j c , of Sm-Ba-Cu-O coated conductors were obtained in the Sm-rich, Ba-poor and Cu-rich composition regions, as compared to the stoichiometric region.…”

Section: Introductionmentioning

confidence: 99%