Mechanisms of limitation and nature of field dependence of critical current in HTS epitaxial YBaCUO films

Pan, V. M.; Пашицкий, Э. А.; Ryabchenko, S. M.; Komashko, V. A.; Pan, Alexey V.; Dou, Shi Xue; Семенов, А.; Tretiatchenko, C.G.; Fedotov, Yu. V.

doi:10.1109/tasc.2003.812523

Cited by 30 publications

(39 citation statements)

References 11 publications

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“…The discretion of LAB's, which consist of dislocations with normal cores separated by the distance d, should be taken into account for a good quantitative description of the experimental J c ͑H͒ curves at an applied field above 1 T. 18,22,30 This can be done by introducing a geometrical factor f(d / ͑2␦͒),…”

Section: ͑19͒mentioning

confidence: 99%

“…15 Such a controversy of observed experimental results is particularly important to be clarified for finding an optimal approach to enhance the critical current density in RBa 2 Cu 3 O 7−␦ materials ͑R is a rare-earth element͒, which can be used, for example, for the development of coated conductors. 14, 15 We have analyzed numerous experimental results of our previous studies, [16][17][18] in which a dominant contribution of extended linear defects to vortex pinning and critical current in YBCO films had become apparent, and developed a consistent model presented in this work. The out-of-plane edge dislocations, emerging during the epitaxial growth of YBCO films and forming low-angle tilt domain boundaries ͑LAB's͒ between single-crystal domains, appear to be the most effective pins for Abrikosov vortex line lattice ͑VLL͒.…”

Section: Introductionmentioning

confidence: 99%

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Supercurrent transport inYBa2Cu3O7−δepitaxial thin films in a dc magnetic field

et al. 2006

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Magnetic field and angle dependences of the critical current density J c ͑H , ͒ in epitaxial c-oriented YBa 2 Cu 3 O 7−␦ thin films are measured by the four-probe transport current technique, low-frequency ac magnetic susceptibility, and superconducting quantum interference device magnetometry. The films under study are deposited by off-axis dc magnetron sputtering onto r-cut sapphire substrates buffered with a CeO 2 layer. A consistent model of vortex pining and supercurrent limitation is developed and discussed. Rows of growthinduced out-of-plane edge dislocations forming low-angle boundaries ͑LAB's͒ are shown to play a key role in achievement of the highest critical current density J c ജ 2 ϫ 10 6 A/cm 2 at 77 K. The model takes into account the transparency of LAB's for supercurrent as well as the pinning of vortex lattice on a network of LAB's. Principal statistical parameters of the film defect structure, such as the domain size distribution and mean misorientation angle, are extracted from J c ͑H͒ curves measured in a magnetic field H applied parallel to the c axis and from x-ray diffraction data. An evolution of angle dependences J c ͑͒ with H is shown to be consistent with the model supposing dominant pinning on edge dislocations. Strongly pinned vortices parallel to the c axis appear to exist in tilted low magnetic fields up to a characteristic threshold field, below which the magnetic induction within the film obeys a simple relation B = H cos . This feature is shown to explain the absence of the expected maximum of J c ͑͒ at H ʈ c in a low applied field. A peak of J c ͑H͒ and an angular hysteresis of J c ͑͒, which have been observed in an intermediate-field range, are discussed in terms of film thickness, surface quality, and orientation of the applied field. The observed effects are found to be consistent with the developed model. DOI: 10.1103/PhysRevB.73.054508 PACS number͑s͒: 74.25.Sv, 74.72.Bk, 74.78.Bz lated disorder ͑e.g., by random pointlike pins͒, the J c ͑H , ͒ dependence is determined by a single parameter H͑cos 2 + 2 sin 2 ͒ 1/2 , 12,13 where = ͱ m ab / m c is the anisotropy parameter, =1/5-1/7 for YBCO. For the monotonic decreasing J c ͑H , =0͒ dependence the scaling naturally yields the J c ͑H = const, ͒ dependence with a minimum at = 0 and a maximum at = /2.Moreover, a maximum of the J c ͑H , ͒ dependence at H ʈ c was shown ͑e.g., Ref. 6͒ to be absent for YBCO films. Ironically, many researchers considered this observation to be strong evidence for the absence of out-of-plane linear pins or their ineffectiveness for vortex pinning in epitaxial films. In a contrast, recently Maiorov et al. have observed the J c ͑H , ͒ peak at H ʈ c. 14 The maximum does exist and tends to shift PHYSICAL REVIEW B 73, 054508 ͑2006͒

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Section: ͑19͒mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Supercurrent transport inYBa2Cu3O7−δepitaxial thin films in a dc magnetic field

et al. 2006

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“…[1][2][3][4][5] The value of B * has been suggested to be governed by the most effective linear defects. Pinning of vortices on these defects leads to a matching effect, which occurs when the number of vortices corresponds to the number of linear defects in films.…”

mentioning

confidence: 99%

“…This indicates that ͑i͒ the "effective" pinning for individual vortices at B a ഛ B * is not necessarily the same as in the collective ͑FLL͒ pinning region ͑B a Ͼ B * ͒; ͑ii͒ J c at B a ഛ B * is mainly restricted by the transparency of supercurrent paths ͑via grain boundaries͒, not by the pinning. 4,29 The study of the B * ͑t͒ dependence on has shown that the behavior does not undergo a qualitative change for the HTS samples measured ͓Fig. 3͑b͒ and 3͑c͔͒.…”

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confidence: 99%

Comparison of small-field behavior inMgB2, Low- and high-temperature superconductors

Pan

Dou

2006

Phys. Rev. B

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Different types of superconductors have been investigated at small magnetic fields ͑B a ͒ over wide temperature ͑T͒ ranges at different B a orientations. It has been shown that the temperature dependence of the characteristic field ͑B * ͒, separating the B a -independent critical current density ͑J c ͒ plateau ͑single vortex pinning regime͒ and the region with J c ͑B a ͒ ͑collective pinning͒, can be attributed either to the temperature dependence of the magnetic penetration depth for Nb-film and MgB 2 bulk superconductors, or to thermally activated processes for Bi-based superconductors and YBa 2 Cu 3 O 7−␦ superconducting films. In both cases the vortex pinning influence appears to have a secondary role, affecting the effective vortex depinning radius. An exception in such B * ͑T͒ behavior is considered for Nb film when the magnetic field has its considerable component applied perpendicular to the main surface of the film.

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“…17 Eq. ͑2͒ is different from the original model 3,18 as it deals with more flexible and realistic rectangular ͑rather than square͒ shape of the domains. 1 Furthermore, we have introduced a modulated pinning potential along the pinning walls formed by LABs ͓Fig.…”

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Extended dislocation-based pinning mechanism in superconducting YBa2Cu3O7 films

Pysarenko

Pan

Dou

et al. 2010

Journal of Applied Physics

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To describe the critical current density ͑J c ͒ as the function of applied magnetic field ͑B a ͒ in high quality YBa 2 Cu 3 O 7 ͑YBCO͒ superconducting films, the vortex pinning mechanism along the structural domain boundaries of the films is developed. The boundaries, assumed to have low misorientation angles, are quantitatively considered to consist of individual edge dislocations acting as pinning wells, rather than a continuous boundary. This extended model accurately describes the experimental J c ͑B a ͒ over the wide field and temperature ranges. Marginal deviations of the model from the experimental J c ͑B a ͒ curves are observed at high fields and temperatures where thermally activated depinning is significant. This pinning model is verified to provide precise structural properties of the films which can be obtained by other considerations.Understanding of electromagnetic behavior of YBa 2 Cu 3 O 7 ͑YBCO͒ superconducting thin films at applied magnetic field ͑B a ͒ is important task of theoretical and experimental physics. Numerous attempts 1-3 to describe pinning mechanisms resulting in high J c have led to controversial conclusions on the origin of the strong pinning in the films. The successful model 3 working over the entire B a range has been proposed on the basis of the experimental evidence 1,4,5 indicating the significant contribution of the linear defects ͑dislocations͒ to vortex pinning. Indeed, this type of defects can pin vortices along their entire length, providing the strongest available pinning. 6-8 The other successful model 9,10 is based on the only assumption of the network of Josephson junctions governing J c ͑B a ͒ dependence in YBCO films. This assumption is unlikely to be the case in the quality YBCO films with high J c having low angle boundaries between structural domains. 11 In Ref. 3, it was assumed that the vortices are effectively pinned on out-of-plane extended defects ͓edge dislocations ͑EDs͔͒, which form a network of structural domains separated by low angle boundaries ͑LABs͒. This model deals with statistical domain size distribution and the pinning width ␦ c , 12,13 which characterizes the width of pinning walls formed by LABs. Basic idea is to calculate the probability to pin vortices, which form a flux-line lattice ͑FLL͒, by trapping them within the range ␦ Յ ␦ c .Real YBCO films demonstrate not only different domain size distribution, but also different low angles between these domains. Different angles between domains imply different spacing d between the EDs, which govern J c in the films. 11 The spacing d has been qualitatively mentioned in the original model, however, the quantitative approach has not been developed.In this work, we have substantially extended the statistical model by introducing more realistic the modulated pinning landscape along LABs and the rectangular ͑rather than square͒ shape of the domains. It has allowed us to explain the behavior of J c ͑B a ͒ curves with a better accuracy in the low and intermediate B a regions. Comparison of two slightly ...

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Mechanisms of limitation and nature of field dependence of critical current in HTS epitaxial YBaCUO films

Cited by 30 publications

References 11 publications

Supercurrent transport inYBa2Cu3O7−δepitaxial thin films in a dc magnetic field

Supercurrent transport inYBa2Cu3O7−δepitaxial thin films in a dc magnetic field

Comparison of small-field behavior inMgB2, Low- and high-temperature superconductors

Extended dislocation-based pinning mechanism in superconducting YBa2Cu3O7 films

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