Experimental analysis of the magnetic field shielding and trapping properties of bulk melt-processed YBa2Cu3O7−δ

Jiang, Xiaohua; Astill, D. M.; Lo, Wai; Cardwell, D. A.; Coombs, Tim; Campbell, A.M.; Larsen, Jørgen Gutzon

doi:10.1016/0921-4534(95)00262-6

Cited by 13 publications

(11 citation statements)

References 6 publications

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“…This was achieved by zero-field cooling ͑ZFC͒ and then subjecting the sample to an increasing magnetic field, ramped linearly for 0.05 s to some value exceeding twice the full-penetration field. 64 H z is then decreased towards zero at the same sweep rate. A constant time interval ͑10 s͒ was then employed in order to allow the trapped magnetic moment to relax due to flux creep effects.…”

Section: Modelmentioning

confidence: 99%

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

et al. 2007

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Crossed-magnetic-field effects on bulk high-temperature superconductors have been studied both experimentally and numerically. The sample geometry investigated involves finite-size effects along both ͑crossed-͒ magnetic-field directions. The experiments were carried out on bulk melt-processed Y-Ba-Cu-O single domains that had been premagnetized with the applied field parallel to their shortest direction ͑i.e., the c axis͒ and then subjected to several cycles of the application of a transverse magnetic field parallel to the sample ab plane. The magnetic properties were measured using orthogonal pickup coils, a Hall probe placed against the sample surface, and magneto-optical imaging. We show that all principal features of the experimental data can be reproduced qualitatively using a two-dimensional finite-element numerical model based on an E-J power law and in which the current density flows perpendicularly to the plane within which the two components of magnetic field are varied. The results of this study suggest that the suppression of the magnetic moment under the action of a transverse field can be predicted successfully by ignoring the existence of flux-free configurations or flux-cutting effects. These investigations show that the observed decay in magnetization results from the intricate modification of current distribution within the sample cross section. The current amplitude is altered significantly only if a field-dependent critical current density J c ͑B͒ is assumed. Our model is shown to be quite appropriate to describe the cross-flow effects in bulk superconductors. It is also shown that this model does not predict any saturation of the magnetic induction, even after a large number ͑ϳ100͒ of transverse field cycles. These features are shown to be consistent with the experimental data.

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Section: Modelmentioning

confidence: 99%

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

et al. 2007

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“…This difference can be explained by the fact that the size of the inhomogeneities in our samples is lower as the resolution of the mapping device. Also in [14] the inhomogeneities of the shielded fields above the textured samples have been highly pronounced, however, at external magnetic fields, which were two orders higher than in this work. Figure 3 shows the ac magnetisation M vs. the applied field H0 (corrected by the demagnetisation factor) of the sample fabricated by the PMP technique for five magnetisation field amplitudes.…”

Section: Resultsmentioning

confidence: 45%

Magnetic Properties of YBa₂Cu₃O_7-δMelt Textured Samples Prepared by Powder Melting Process and Quench and Melt Growth Techniques

et al. 2000

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The microstructure and magnetic properties of the melt textured YBa2Cu3O7_δ samples prepared by the powder melting process, in which Y2Cu2O5 and BaCuO2 were used as precursors, and those prepared by the quench aud melt growth method are described and compared. The lattice parameters and Tc values for the samples prepared by the both techniques were similar. The penetration and the spatial distribution of the magnetic flux in the superconducting samples was imaged by means of a field-mapping device using a Hall probe. In the range of low magnetic fields up to 820 A m-1 no significant differences in penetration of magnetic flux between the samples prepared by the powder melting process and the quench and melt growth were observed. The mapping could not resolve any grain boundaries, single grains and structural defects. By the ac and virgin volume magnetisation characteristics, which were measured in the zero-field cooled condition by a 2nd order SQUID gradiometer, no weak links were identified. Better magnetic properties of the quench and melt growth samples in high magnetic fields can be explained by the differences in microstructure and/or by the risen content of the finely dispersed 211 and Pt containing phases. The increase factor in magnetisation is about 2.5. Some aspects of the Bean model for textured YBa2Cu3O7-δ samples are discussed.

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“…Two possible scenarios prevail for a gain boundary or joint in the presence of an applied magnetic field. If the flux pinning force at the joint is weak and the critical current low, magnetic flux will penetrate readily between the grains and they will behave like two separate specimens [33]. However, this is not observed from the magnetic field distribution in Fig.…”

Section: Fig 7 a Sem Micrograph Showing The Non-uniform Growth Fronmentioning

confidence: 59%

“…This shows a Hall probe map of the surface of two YBCO grains joined along their c-axis (i.e. with effectively no mismatch angle) in an external magnetic field of 10 mT in a field screening arrangement [33]. The position of the grains and the boundary and the magnitude of the field normal to the sample surface are indicated in the diagram.…”

Section: Fig 7 a Sem Micrograph Showing The Non-uniform Growth Fronmentioning

confidence: 99%

Growth features and intergranular connectivity of melt processed YBCO

Lo¹,

Dewhurst²,

Cardwell³

et al. 1996

Applied Superconductivity

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Large grain melt processed Y-Ba-Cu-O (YBCO) samples have been prepared by seeded and unseeded growth techniques. The current carrying ability within individual grains and across grain boundaries has been investigated and correlated with features in the microstructure of samples fabricated by both techniques. The development of an inhomogeneous, cell-like growth microstructure in seeded samples at distances ≈4 mm from the seed is related to a saturation in inclusion density and volume proportion of Y 2 BaCuO 5 (Y211) particles. A significant decrease in critical current density is associated with this change over a wide temperature range. The resistance of high angle c-axis grain boundaries is observed to depend critically on the magnitude of the injection current whereas the intragranular resistance is not influenced significantly by this variable. J c of a grain boundary fabricated by unseeded melt growth is estimated to be less than 100 A cm -2 at 77 K in zero applied field, which is more than two orders of magnitude lower than the intragranular J c . Field screening measurements suggest that low angle grain boundaries do not form weak links between grains in modest magnetic fields and hence do not present a significant barrier to current flow.

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Experimental analysis of the magnetic field shielding and trapping properties of bulk melt-processed YBa2Cu3O7−δ

Cited by 13 publications

References 6 publications

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

Magnetic Properties of YBa₂Cu₃O_7-δMelt Textured Samples Prepared by Powder Melting Process and Quench and Melt Growth Techniques

Growth features and intergranular connectivity of melt processed YBCO

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Experimental analysis of the magnetic field shielding and trapping properties of bulk melt-processed YBa2Cu3O7−δ

Cited by 13 publications

References 6 publications

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

Magnetic Properties of YBa2Cu3O7-δMelt Textured Samples Prepared by Powder Melting Process and Quench and Melt Growth Techniques

Growth features and intergranular connectivity of melt processed YBCO

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Magnetic Properties of YBa₂Cu₃O_7-δMelt Textured Samples Prepared by Powder Melting Process and Quench and Melt Growth Techniques