Abstract: A magnetoresistive detector comprising a stack of layers having different magnetic characteristics (magnetic metal multilayers) wherein there is provision, under the effect of an electrical field, for a transfer of electrons perpendicularly to the layers. To ensure several perpendicular transfers through the same stack of layers, this stack is enclosed between two electrodes, and the electrical conduction of the entire piece is interrupted by a cutting out of the structure in the form of teeth in a Greek key pattern.

Abstract: Field effect transistors are provided and more particularly those which work at very high frequencies.According to the invention the field effect transistor has a vertical structure, comprising an access electrode, source or drain, on each of the two faces of the substrate wafer. The gate is formed by an N type epitaxial layer thickness sandwiched between two N.sup.+ type layers. The gate thickness is then limited by the epitaxial layer thickness which can be obtained of the order of a few hundred angstroms. The gate contact is taken by means of lateral metal layers, on the chamfered sides of the epitaxial layer.

Abstract: A system for automatic regulation of the density of a given molecular type at a pre-arranged point in an apparatus called a "flux or molecular jet", intended to make epitaxy layers. In a vacuum enclosure a probe for mass spectrometry analysis (electrostatic, four pole apparatus) picks up the types projected by evaporating units, ionizes them, filters and detects them as a function of their respective masses. The heating in each unit is regulated by a servo-control loop which contains means for analyzing the type concerned.