Pinning Force Films

Przyslupski et al. (1979) have prepared by dc sputtering thin films such as LaMoeSg. They are annealed in the range of temperatures from 290 up to 1320 K. The transition temperatures have been measured as 6.2 and 5.4 K (11.4K for bulk material). The sample properties have been studied in magnetic fields up to 8 T and in the temperature range 1.7-4.2 K. The curves of the critical current and of the pinning force density show a highest critical current density reached for B = 0 and T = 1.7 K, with L = 1.7 x 10 A m . 

From measurements of pinning force densities on thin-film samples of NbaGe and NbsGa with known microstructure, results were obtained which are compared with existing pinning theories. 

The results for one representative NbsGe film prepared by sputtering are presented in Fig. 1. For temperatures between 19 and 4 K, the maximum pinning force density is [BdiT)]. The reduced pinning force density follows... 

Fig. 1. (a) Log-log plot of the maximum pinning force density for a cosputtered NbaGe film vs. the upper critical magnetic induction in parallel and perpendicular fields. The curve has a slope of f. (b) Pinning force density relative to its maximum value as a function of the reduced magnetic induction, b = B /Bcw or b = BjBci., at different temperatures. 

Figure 8 shows H2SO4 droplets on mica at very low humidity (<5%). The contact line aronnd the drops is smooth and circnlar, revealing that no pinning has occurred [49]. Although the area between drops is flat, it does not correspond to clean mica but to a liquid film covering it of a few monolayers thickness. This is deduced from the hysteresis in the force versns distance experiments, where the tip is brought into contact with the surface and then pulled off. 

As the stamp is gently placed in contact with a solution spread on a substrate, capillary forces drive the solution to form menisci under the stamp protrusions. The solution remains pinned to the protrusions upon solvent evaporation. As the critical concentration is reached, the solute precipitates from solution onto the substrate, giving rise to a structured thin film replicating the protrusion of the stamp. By optimizing the conditions, it is possible to print isolated structures with a size comparable to or even smaller than the lateral width of the stamp protrusions,... 

Fig. 5. Apparatus used to measure Young s modulus and Poisson ratio of gel films. AM anglemeter, LB bar to apply a longitudinal force, W weight, TB bar to detect thickness change, M mirror, S fulcrum, FB fixed bar, F gel film, TW weight to apply preload on gel film through pins...

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