Thermo-magnetic stability of superconducting films controlled by nano-morphology

Abstract

, T. H. (2013). Thermo-magnetic stability of superconducting films controlled by nano-morphology. Applied Physics Letters, 102 (25), 252601-1-252601-5.

Dendritic flux avalanches in high-quality NbN superconducting films

“…From this point of view, the origin of dendritic instabilities would remain unexplained. However, independent scanning electron microscopy (SEM) study in [8] showed that, seemingly in correlation with Tc and ρn, one of the films showed granular nanostructure, and another did not. It was the film with welldefined nano-grains that demonstrated dendritic instabilities.…”

“…This behaviour is unexpected. The film has parameters such as critical temperature or resistivity much better than in any NbN films deposited previously, and according to [8], it should not show dendritic instabilities.…”

“…In [8], comparing two films with different Tc and ρn, it was assumed that improvement in these parameters leads to stable flux penetration into the film. In contrast, theoretical analysis in the same work showed that both films investigated in it should be thermo-magnetically stable.…”

“…Ideally, however, would be not to have dendritic instabilities in the film at all. In [8] a NbN film intrinsically free from avalanches was demonstrated. The film was prepared by an epitaxial growth and had high Tc and low n, which are usually considered as features of high-quality films.…”

A radio-frequency coil for the microwave characterization of vortex dynamics in thin film superconductors

“…Moreover, nano-scaled defects, which enhance the critical current density and the Joule heating, have proven to favor the development of vortex instabilities in the form of quasi-one-dimensional micro-jumps in nano-granular samples of NbN due to the rise of the local electrical fields. 72 In addition to the experimental particularities and previous results mentioned above, and in order to shed light on any possible contribution from the MW electric and magnetic fields to the observed jump-like magnetic response, the values of the parallel and perpendicular components of E and H were estimated at the edge of the CS. The results obtained for constant values of referent nominal power (P = 0 dBm), frequency value ( f = 1.06 GHz), and Q factor (50) were found to be E ∥ ≃ 1000 V/m, E ⊥ ≃ 850 V/m, and H ∥ ≈ H ⊥ ≃ 0.1 Oe.…”