Magnet structure for nuclear magnetic resonance imaging apparatus

A magnet structure for Nuclear Magnetic Resonance imaging apparatus, which magnet structure has at least two opposing magnetic pole pieces (1), which are located at a certain distance from each other and delimit an imaging region, which pole pieces (1) are formed by at least one massive layer (201) of a magnetically permeable material, and at least one layer of magnetically permeable material consisting of a pack of superimposed sheets (2,2') or foils, electrically insulated from each other, each of which sheets has cuts (102,102') arranged over the surface of the sheet (2,2') in positions that are non coincident with the cuts (102,102') of one or both adjacent sheets (2'). The magnetically permeable sheets or foils (2,2') have a first face and a second face and the cuts (102,102') have a width and a length and are arranged on each sheet (2,2'), that the cuts (102,102') of a sheet or foil (2) are offset and not coincident with respect to the cuts (102,102') of the adjacent sheet or foil (2'), when said adjacent sheet (2') is laid over the previous sheet (2) in an overturned position, i.e. with the first face turned toward the first face of the first sheet (2) or with the second face of said adjacent sheet (2') turned toward the second face of the first sheet (2).