Critical state stability in type-II superconductors and superconducting-normal-metal composites

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB2bulk samples

“…A condition needed for flux jumps to occur is that the first flux jump field H fj (T ) is placed below the full penetration field [39,40], which may be experimentally approximated by the first peak field H fp (T ). So, when H fj (T ) < H fp (T ) flux jumps are expected while above a characteristic temperature T o , where…”

Controllable morphology of flux avalanches in microstructured superconductors

“…A viable alternative to obtain information about the spatial and temporal evolution of the dendritic flux avalanches is to carry out simulations of their dynamics. The origin of dendritic avalanches in superconducting films is a thermomagnetic instability mechanism due to the Joule heating created by vortex motion and the consequent reduction of the critical current density as the temperature increases [5,35]. The instability is also a consequence of the nonlinear material characteristics of type II superconductors, which is conventionally approximated by a power law…”

“…Although the physics behind the propagation of cracks, dielectric breakdowns, and flux avalanches, have been extensively studied in uniform media [2][3][4][5][6][7], little is known about the pattern formation in the case of periodic variations in the properties of the host material. In particular, one can then pose the question as to whether the morphology of flux avalanches is reflecting microscopic properties of the matrix or, inversely, if by introducing modulations on the material properties one would be able to impose a particular shape to the ubiquitous multi-branching splitting of avalanches.…”

Enhanced pinning in superconducting thin films with graded pinning landscapes

“…6 It has been demonstrated that the insertion of arrays of ADs in a superconducting film can lead, at high temperatures, to an increase of the critical current. 6 Unfortunately, at low temperatures, such PCs facilitate the proliferation of flux channeling [7][8][9][10] leading to unwanted instabilities of thermomagnetic origin 11,12 which render the superconductor impractical. A good compromise between strong pinning and lack of channeling can be achieved by introducing a quasiperiodic array of PCs, as suggested theoretically by Misko et al [13][14][15] and confirmed experimentally by Kemmler et al 16 and Silhanek et al 17 This aperiodic distribution of pinning centers may be further optimized by matching it to the typically non-uniform distribution of vortices.…”