Role of the twin boundary for the occurrence of peak effect in Y-Ba-Cu-O superconducting bulks melt grown under varied oxygen pressure

Abstract

A novel melt-growth technique, i.e. melt growth under varied oxygen pressure (MGVOP) in which the oxygen partial pressure is increased to solidify the initial melt, has been employed to prepare melt-textured superconducting bulks of the Y-Ba-Cu-O system. The obtained textured bulk samples consisted of two phases, i.e. superconducting and non-superconducting (Y-211). The critical current density of the samples reached as high as 40 kA (at 65 K) at a high magnetic field of T to exhibit a peak in the versus relation, i.e. a peak effect. To elucidate the causes of the peak effect and the high values of at high magnetic fields, submicron structures of the MGVOP-processed samples were examined by transmission electron microscopy (TEM), and the distributions of both Y-211 particles and twin boundaries were studied. In order to collect sufficient data for statistical analyses, specimens for `large-area TEM observations' were prepared using a focused ion beam thinning technique such that the TEM-observable area of the specimen was as wide as . Statistical analyses of the TEM images yielded the volume fraction of Y-211 phase, the average size of Y-211 grains and the inter-twin-boundary distance for each sample. It was concluded that a sample that had a higher twin-boundary density possessed a higher value at the peak in the versus characteristics, while fine Y-211 particles were likely to contribute to the value only at low magnetic fields.

Evidence of pinning crossover and the role of twin boundaries in the peak effect in FeSeTe iron based superconductor

“…For fields lower than 3 T, the strong pinning model starts to fail to describe satisfactorily the behavior of our data, its fits getting worse as the magnetic field decreases. It is important to underline that the morphological analysis performed on our sample (and on samples from the same batch) effectively confirms the presence of correlated disorder in terms of twin boundaries [31,32,46,81] (see figure 8), which can act as strong pinning centers at high field in particular, where the point-like defects are not effective anymore.…”

“…The correlation between peak effect and twin boundaries was already hypothesized for cuprates [81][82][83] and other IBSs [42,84]. In this work, in addition to showing that this correlation exists for the FeSeTe superconductor, the role of the twin boundaries in the dynamical mechanism that produces the peak effect has been detected and described, by means of different pinning models corresponding to different field ranges.…”

Crossover between Channeling and Pinning at Twin Boundaries inYBa2Cu3O7Thin Films

“…1(a) near the channeling minima. We have taken a value of d tb 5 nm, typical for YBCO [27], and left f k and f cut as fitting parameters. Solid lines in Fig.…”

Twin boundary energy and characterization of charge redistribution near the twin boundaries of cupperate superconductors

“…The generated smallest super-cell (with TW$5 Å) for modeling a (1 1 0) twin boundary in the YBCO system will be chosen according to the high resolution electron microscopy (HREM) images [38] and will consist of 7 layers along the c direction and includes 52 atoms in total, Fig. 1A and B.…”