A method for manufacturing a spin injector device, comprising the following steps of: a) forming a metal protection layer on a face of a substrate, so as to restrict or prevent oxidation and/or contamination of said face by its environment, the face being magnetic and electrically conductive, the protection layer being of a diamagnetic or paramagnetic nature; b) forming an upper layer onto the protection layer, able to promote a spin bias of electronics sates in the vicinity of the Fermi level of the interface between the protection layer and the upper layer according to an amplitude and a spin referential frame which are defined by the magnetism of the substrate and/or of the face of the substrate, the upper layer being an organic layer of which one or more molecular sites have, in contact with the protection layer, a paramagnetic moment.