Remanence is the residual magnetism that a previously magnetized material retains after the magnetic field is removed. This is due to the fact that during magnetization the molecular magnets are aligned and remain in their position afterwards.
The residual magnetism is compensated only by an opposite magnetization with coercive force.
The remanence forms the basis for all storage processes that work with ferromagnetic materials, such as magnetic tapes, magnetic disks and floppy disks. In these processes, the magnetic oxide crystals are magnetized and aligned during recording; after removal of the magnetic field, the particles retain their remanence, which is inductively detected during readout via the playback heads.