A magnetic bearing for the mounting of a shaft (7), in particular for a spinning rotor of an open-end spinning device, features several pole shanks (2) of a stator (1) for the active radial magnetic mounting of the shaft (7) in two degrees of freedom, which in each case are surrounded by a coil (6) and are radially arranged to each other, whereas the pole shanks (2) are arranged at each other in such a manner that they release an opening (4) for the shaft (7). In the area of the opening (4), and on the side of the coils (6) turned away from the opening (4), the pole shanks (2) are connected to each other. In particular, for the passive axial mounting of the shaft (7), at least one permanent magnet (10) is arranged between the coils (6) and the opening (4); this is in operative connection with the pole shanks (2). A shaft (7) for mounting with at least one corresponding magnetic bearing is a composite component, which at least partially consists of non ferromagnetic material. In the area of the radial and (if applicable) axial mounting, a component made of a ferromagnetic material is arranged. A shaft mounting, in particular for a rotatable shaft of a spinning rotor in an open-end spinning device, features, for the passive axial mounting of one degree of freedom of the shaft (7) and for the active radial mounting of two degrees of freedom of the shaft (7), at least one, preferably two, corresponding magnetic bearings.