Imaging Flux Avalanches in V$_3$Si Superconducting Thin Films

Abstract

When developing superconducting devices patterned on thin films one should bear in mind that flux avalanches might occur for some materials at a certain window of applied fields and temperatures. Although the A15 superconductors are well known and used in a variety of purposes, there are no studies about flux avalanches in V3Si thin films. In the present work we report the observation of flux avalanches in films of V3Si, grown by Pulsed Laser Deposition on a LaAlO3 substrate. The range of temperatures and applied magnetic fields at which the avalanches take place was determined using dc-magnetometry. Magneto-Optical Imaging was employed to visualize the occurrence and spatial distribution of such flux avalanches. Images of the flux penetrated into the samples indicate a clear anisotropic distribution, which is ascribed to a thickness gradient. The observation of flux avalanches reported here imply that attention to this feature must be given when films of V3Si are envisaged for possible applications.

Magnetic flux penetration in nanoscale wedge-shaped superconducting thin films

“…It is important mentioning that two flourishing patterns on the bottom left edge are due to defects, which favor the flux penetration around them [69] and produce a minor distortion of the central d line and a slight asymmetry of the side borders. This type of nonuniform flux penetration due to a thickness variation has been also observed in a V 3 Si film [70]. Figure 2(e) shows examples of the spatial profile of the induction component B z taken for different applied fields, being obtained from the average on a 208-μm-wide strip around the colored horizontal dashed lines depicted in Figs.…”

“…The elemental composition of a given material can be obtained from its EDS spectra [98]. As the detected energy intensity depends on the initial electron beam energy and the average volume of the droplet-shaped interaction region, EDS may also be employed to estimate the film thickness [70,[99][100][101][102]. Most authors use the relation I f /I s ∼ d, where I s (I f ) is the peak intensity of the substrate (film), to obtain the thickness.…”

Controlling magnetic flux penetration in low-T C superconducting films and hybrids

“…The dendritic flux avalanches have been observed in several materials: Nb [71,72], Nb 3 Sn [73], YBCO [74,75], YNi 2 B 2 C [76], a-MoGe [77], NbN [78], MgB 2 [70], MoSi [79], V 3 Si [80], and Pb [24,81]. Using appropriate lenses, flux avalanches in superconducting films can be entirely observed by means of MOI.…”

Dendritic flux avalanches in superconducting hybrid structures

“…Type-II superconducting films exposed to magnetic fields often exhibit magnetic instabilities in the form of flux avalanches, where abrupt bursts of magnetic flux invade the superconductor through narrow regions, forming dendritic structures [1][2][3][4][5][6][7][8][9][10][11][12]. As magnetic flux instabilities limit potential applications of superconductors in practical devices [13,14], a study of metal coated superconducting films was initiated as a possible way to suppress dendritic avalanches.…”