Abstract: A magnetic decoupler for use with an antitheft device is disclosed. In one preferred embodiment, the decoupler includes a composite permanent magnet comprising an annular permanent magnet that may be of ceramic and a second, preferably disc-shaped permanent magnet, which is preferably more strongly magnetized than the annular magnet and which preferably comprises a rare earth element. The two magnets are coaxially aligned with but axially displaced from each other and are oriented with the opposite polarity so as to create a region of especially great magnetic flux in the bore of the annular magnet. A cover plate, preferably of cold-rolled steel, may be provided adjacent the face of the annular magnet that is remote from the second magnet to further concentrate the flux in the bore.