Mesures sur les propriétés électriques et magnétiques de couches minces à basse température

Abstract
A brief report is given of our earlier measurements on the electrical and magnetic properties of nickel - and ironfilms at low temperatures. So are briefly discussed the dependency of the resistance on the current together with the change of the resistance under the influence of a longitudinal magnetic field (parallel to the current). From these measurements we determined the coercive force and its variation with temperature. We also discuss our earlier measurements on the superconductivity of tin film obtained by cathodic sputtering. The essential properties of these films are : 1) the transmition temperature is higher than for bulk tin. ; 2) the values for the magnetic threshold field (Hc) are much higher than for bulk material. The same can be said from the critical value of the current density i c Silsbee rule can not be considered as valid for the relation between Hc and ic. 3) By increasing the current, the form of the transition curve changes. The curves become more sharp by increasing the current. 4) A large différence is found between the value of Hc - transversal parallel to the film and Hc - transversal perpendicular. New measurements have now been done on nickel - and tin films condensed in vacuum (10-6 mm Hg). For some of our tin films the support was kept at a temperature of liquid air during the condensation. A special technique is described for the manipulation of those films. The tin film condensed at room temperature have the same transition temperature as the bulk metal, while the cooled film have a transition temperature which is much higher. Wespecially investigated the ratio between the transversal parallel threshold field and the transversal perpendicula one. A strong variation is found for this ratio as a function of temperature. This can be explained by considering the anisotropy of tin crystals. Also for our nickel film we measured now in the two field directions. Also we found à large difference, which can be explained by considering the anisotropy factor for nickel crystals and by supposing that the films are formed of crystals with the (110) plane parallel to the plane of the film.