The invention concerns a magnetocaloric device, especially a magnetic refrigerator, a heat pump or a magnetic power conversion machine comprising at least a permanent magnet assembly (4, 11) for generating magnetic flux, a rotating ring (2) coaxially disposed to the permanent magnet assembly, a structure containing magnetocaloric material mounted inside the rotating ring (2) and means for conducting a working fluid through the rotating ring (2). The permanent magnet assembly (4, 11) comprises a set of permanent magnets and at least one insert of highly permeable material (1, 9) attached to the magnet assembly (4, 11) adapted for creating high magnetic flux densities around and inside of the rotating ring (2).