Critical Current Density of HTS Single Crystal YBCO Thin Films in Applied dc Field

Cherpak, Y.V.; Komashko, V. A.; Pozigun, S.A.; Семенов, А.; Tretiatchenko, C.G.; Пашицкий, Э. А.; Pan, V. M.

doi:10.1109/tasc.2005.848212

Cited by 12 publications

(2 citation statements)

References 19 publications

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“…Indeed, it is known that different authors presented quite different results on the J c ͑͒ behavior, showing either one maximum at = 90°and no maximum at =0 6,32 or two maxima at = 0 and = 90°. 4,25,33 The absence of a J c maximum at = 0-i.e., at H ʈ c-in a number of experimental works was considered as unambiguous evidence against the ED pinning model. We are showing in this work that one or two maxima of J c ͑͒ dependences can be easily observed experimentally under different experimental conditions for the same YBCO film.…”

Section: Angle Dependence Of J C "H…mentioning

confidence: 99%

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: Angle Dependence Of J C "H…mentioning

confidence: 99%

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

et al. 2006

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“…Critical current (I c ) of the HTS coil is affected by density distribution and direction of magnetic field [6]. When the dimension and operating current of the coil is fixed, density distribution and direction of the magnetic field around the coil can be calculated.…”

Section: Introductionmentioning

confidence: 99%

Statistical analysis for HTS coil considering inhomogeneous I_cdistribution of HTS tape

Jin

Lee

et al. 2015

Progress in Superconductivity and Cryogenics

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Critical current of high-temperature superconducting (HTS) coil is influenced by its own self magnetic field. Direction and density distribution of the magnetic field around the coil are fixed after the shape of the coil is decided. If the entire part of the HTS tape has homogeneous I c distribution characteristic, quench would be initiated in fixed location on the coil. However, the actual HTS tape has inhomogeneous I c distribution along the length. If the I c distribution of the HTS tape is known, we can expect the spot within the HTS coil that has the highest probability to initiate the quench. In this paper, I c distribution within the HTS coil under self-field effect is simulated by MATLAB. In the simulation procedure, I c distribution of the entire part of the HTS tape is assume d to follow Gaussian-distribution by central limit theorem. The HTS coil model is divided into several segments, and the critical current of each segment is calculated based on the-generalized Kim model. Single pancake model is simulated and self-field of HTS coil is calculated by Biot-Savart's law. As a result of simulation, quench-initiating spot in the actual HTS coil can be predicted statistically. And that statistical analysis can help detect or protect the quench of the HTS coil.

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Supercurrent density above 106A∕cm2 at 77K in a single-crystal film conductor of the cuprate high-Tc superconductor YBa2Cu3O7−δ—dream or reality?

Pan

2006

Low Temperature Physics

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Supercurrent transport phenomena in c-oriented epitaxial thin films of the the high-Tc superconducting (HTS) cuprate YBa2Cu3O7−δ (YBCO) with a high critical current density Jc(77K)⩾2×106A∕cm2 are investigated by four-probe transport measurements, low-frequency magnetic susceptibility studies, and SQUID magnetometry. The film samples are deposited on a single-crystal sapphire (r-cut) substrates with a CeO2 or LaAlO3(100) buffer layer by off-axis dc magnetron sputtering or pulsed laser ablation. A model of the mechanisms of Abrikosov vortex pinning and supercurrent limitation is developed and discussed by comparing its predictions with the results of measurements of the critical current and its dependence on applied magnetic fields of different strength and orientation and also with nanostructure data obtained by high-resolution transmission electron microscopy and electron diffraction in a backscattering geometry. It is shown that the low-angle subboundaries (LABs) formed between domains with a slight azimuthal misorientation during the epitaxial growth of the film play a key role in the phenomena observed in the transport of supercurrent. The tilt LABs form equidistant ordered rows of edge dislocations with nonsuperconducting cores about 3–4nm in diameter. The dislocation lines in the LABs are parallel to each other and perpendicular to the film plane. The average density of dislocations over the area of the film depends on the real statistics of the random system of LABs and can reach 1011cm−2. Since the diameter of the “normal” core of a dislocation is close to the diameter of the core of an Abrikosov vortex, the elementary pinning force of the vortex to the core of the dislocation is close to the maximum possible. The pinning on dislocation subboundaries has the following characteristics: 1) the achievement of high values Jc(77K)⩾2×106A∕cm2 and Jc(20K)>107A∕cm2 in epitaxial films and conductors; 2) the existence of a “plateau” on the Jc(H) curve, i.e., Jc(H)=const for H<Hm; 3) a logarithmic decline of Jc(H) for H>Hm, i.e., at the transition from the single-particle pinning regime to the collective pinning of the vortex lattice on the statistical ensemble of randomly distributed dislocation subboundaries; 4) the existence of a threshold field Hp that determines the limit up to which the vortices in a thin film (d⩽λ) remain rectilinear and perpendicular to the film even in a field inclined at a large angle; 5) the evolution of the angle dependence of Jc(θ) with a change of field strength is in complete agreement with the model of dominant pinning on “threading” edge dislocations. A new “peak effect”—an increase of Jc(H‖ab) with increasing longitudinal field—is observed for the first time for H>Hm, i.e, after the end of the “plateau” Jc(H‖ab)=const.

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Critical Current Density of HTS Single Crystal YBCO Thin Films in Applied dc Field

Cited by 12 publications

References 19 publications

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

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

Statistical analysis for HTS coil considering inhomogeneous I_cdistribution of HTS tape

Supercurrent density above 106A∕cm2 at 77K in a single-crystal film conductor of the cuprate high-Tc superconductor YBa2Cu3O7−δ—dream or reality?

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Critical Current Density of HTS Single Crystal YBCO Thin Films in Applied dc Field

Cited by 12 publications

References 19 publications

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

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

Statistical analysis for HTS coil considering inhomogeneous Icdistribution of HTS tape

Supercurrent density above 106A∕cm2 at 77K in a single-crystal film conductor of the cuprate high-Tc superconductor YBa2Cu3O7−δ—dream or reality?

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Statistical analysis for HTS coil considering inhomogeneous I_cdistribution of HTS tape