Patent ID: 6114719
Filing Date: 2000-09-05
Classification: G11C,H01L

Abstract:
A magnetic tunnel junction memory cell having two magnetic states and usable in a nonvolatile magnetic memory array of memory cells, the array being connected to read/write circuitry for altering and detecting the magnetic state of individual memory cells in the array, the memory cell comprising:a first electrically conductive lead;a magnetic tunnel junction stack formed on the first lead and comprising a fixed ferromagnetic layer having its magnetic moment fixed in a preferred direction in the presence of an applied magnetic field caused by current from the read/write circuitry, an insulating tunnel barrier layer in contact with the fixed ferromagnetic layer, a free ferromagnetic layer in contact with the insulating tunnel barrier layer and whose magnetic moment is free to rotate between directions generally parallel and antiparallel to the magnetic moment of the fixed ferromagnetic layer when exposed to an applied magnetic field caused by current from the read/write circuitry, and a biasing ferromagnetic layer for biasing the magnetic moment of the free ferromagnetic layer in a preferred direction in the absence of an applied magnetic field; anda second electrically conductive lead formed on and in contact with the magnetic tunnel junction stack; whereby when the electrical leads are connected to the read/write circuitry, the electrical resistance to current flow through the insulating tunnel barrier layer in a direction generally perpendicular to the fixed and free ferromagnetic layers is determined by said parallel or antiparallel magnetic moment of said free ferromagnetic layer, the value of said electrical resistance thereby allowing the magnetic state of the memory cell to be determined.