Patent ID: 8467222

Claim:
A reader for a magnetic shift register, comprising: a magnetic reference layer, disposed at a first side of a magnetic track of the magnetic shift register as a magnetic pinned layer, for providing a first magnetic field having a first direction to the magnetic track, wherein the magnetic reference layer is electrically connected to a readout circuit; a tunneling layer, disposed between the magnetic reference layer and the magnetic track, for providing a magnetic tunnel junction between the magnetic reference layer and the magnetic track; a magnetic cancelling layer, disposed at a second side of the magnetic track, partially or completely overlapped to the magnetic reference layer in a perpendicular direction of the magnetic track, and providing a second magnetic field having a second direction to the magnetic track, wherein the second direction is opposite to the first direction, and the magnetic cancelling layer is floating; and an isolated layer, disposed between the magnetic cancelling layer and the magnetic track, for blocking a current in the magnetic track from tunneling to the magnetic cancelling layer, wherein the magnetic cancelling layer is synthetic anti-ferromagnetic structures, and the synthetic anti-ferromagnetic structure of the magnetic cancelling layer comprises: a third ferromagnetic layer, disposed at the second side of the magnetic track and the isolated layer, wherein the third ferromagnetic layer is floating, and a magnetic moment direction of the third ferromagnetic layer is the second direction; a second non-magnetic metal layer, disposed between the third ferromagnetic layer and the fourth ferromagnetic layer; and a fourth ferromagnetic layer, disposed between the isolated layer and the second non-magnetic metal layer, and a magnetic moment direction of the fourth ferromagnetic layer is the first direction.