The invention concerns a magnetic field-sensitive component, a magnetic field sensing device and a memory structure each incorporating said component, and a method for detecting a magnetic field using said component. A component according to the invention comprises: at least one diluted magnetic semiconductor, first means for generating an electric current in said semiconductor along one predetermined direction, and second means for producing a signal representing a Hall voltage transverse to said direction, and it is so designed that the semiconductor is selected from the group consisting of II/VI and IV/IV type semiconductors and comprises a zone sensitive to said field which forms all or part of a magnetic quantum well, wherein are confined current carriers incorporated by doping in the semiconductor and inducing in said well ferromagnetic exchange interactions.