4 research outputs found
Very strong intrinsic supercurrent carrying ability and vortex avalanches in (Ba,K)Fe2As2 superconducting single crystals
We report that single crystals of (Ba,K)Fe2As2 with Tc = 32 K have a pinning
potential, U0, as high as 10^4 K, with U0 showing very little field
depend-ence. In addition, the (Ba,K)Fe2As2 single crystals become isotropic at
low temperatures and high magnetic fields, resulting in a very rigid vortex
lattice, even in fields very close to Hc2. The rigid vortices in the two
dimensional (Ba,K)Fe2As2 distinguish this compound from 2D high Tc cuprate
superconductors with 2D vortices, and make it being capable of cearrying very
high critical current.Flux jumping due to high Jc was also observed in large
samples at low temperatures.Comment: 4 pages, 7 figures. submitte
Anisotrophic currents and flux jumps in high-Tc superconducting films with self-organized arrays of planar defects
Regular arrays of planar defects with a period of a few nanometers can be introduced in superconducting YBa2Cu3O7-δ (YBCO) thin films by depositing them on vicinal (also called miscut or tilted) substrates. This results in the anisotropy of critical currents flowing in the plane of the film. We present results of real-time magneto-optical imaging (MOI) of magnetic flux distribution and dynamics in a series of YBCO thin films deposited on NdGaO3 substrates with different miscut angles θ. MOI allows reconstructing the current flow profiles. From the angle formed between domains with different directions of the current flow we determine the anisotropy parameter of the in-plane current, as well as its field and temperature dependences. The artificially introduced defects also have a dramatic effect on the dynamics of the flux propagation: for 10°\u3cθ\u3c14° the magnetic flux propagates along the easy channels intermittently, i.e. in a form of flux jumps. This behavior is indicative of thermo-magnetic instability in superconductors, but we argue that this effect can be of a different nature
Nanosecond voltage pulses from dendritic flux avalanches in superconducting NbN films
Combined voltage and magneto-optical study of magnetic flux flow in superconducting NbN films
is reported. The nanosecond-scale voltage pulses appearing during thermomagnetic avalanches
have been recorded in films partially coated by a metal layer. Simultaneous magneto-optical
imaging and voltage measurements allowed the pulses to be associated with individual flux
branches penetrating the superconductor below the metal coating. From detailed characteristics
of pulse and flux branches, the electrical field in the superconductor is found to be in the range of
5-50 kV/m, while the propagation speed of the avalanche during its final stage is found to be close
to 5 km/s.peerReviewe