Superconducting transitions of Nd-based 123 superconductors in fields up to 7 T

Abstract

Superconducting transitions were measured in field-cooled cooling and field-cooled warming modes in external magnetic fields ranging between 1 mT and 7 T on various Nd-based 123 superconductors (NdBa 2 Cu 3 O 7−δ single crystals and melt-processed samples, and melt-textured ternary compounds). Most of the Nd-based superconductors investigated exhibit a two-step transition when being cooled or warmed in fields larger than 4 T. We ascribe this effect to the presence of an Nd-rich phase providing a spatial scatter of the transition temperature, T c , throughout the sample.

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

“…[5,7]. Similar behaviour was also observed on bulk samples of YBCO [8] and even in Bi-2223 tapes [6]. The consequence of these experiments is that evidently all high-T c superconductors are spatially inhomogeneous; even the "high-quality" crystals.…”

“…Furthermore, nanoscale particles may be added to the precursor powders prior to the heat treatment; many attempts using nanoparticles of Al 2 O 3 [4], MgO [5], Y 2 Ba 4 CuZrO y [6] and even carbon nanotubes [7] are described in the literature. From a variety of magnetic measurements on 123-based and Bi-based high-T c superconductors [8,9], a general flux pinning diagram was deduced [10], showing the interplay of the two basic pinning mechanisms, δT c -and δl-pinning [11]. The δl-pinning mechanism is due to fluctuations of the carrier men free path, while the δT c -pinning is provided by fluctuations of the transition temperature, T c [11].…”

Development of MgB₂-Based Bulk Supermagnets

“…This also reflects the non-scaling of the pinning forces, as the R(T,B) curves correspond to the M(T,B) behavior as discussed in Refs. [18,19].…”

Second Step in the Field-Cooled Magnetization of Bi-2212 Single Crystals

“…Also, in X-ray analysis areas of the size of unit cells may not be detectable. In the NdBCO system, the second step is indeed due to the presence of an Nd-rich phase with weaker superconducting properties [5]. If this second step is of intrinsic nature, there will be no possibility to increase the current densities of the Bi-based superconductors further.…”

“…This ensures a large number of datapoints even in a sharp superconducting transition. More details of the measurement procedure are given in [5]. Figure 1 presents FCC and ZFC-W transitions of the Bi-2212 single crystal.…”