Patent ID: 7973349

Claim:
A magnetic memory device, comprising: a substrate; a magnetic cell configured to have a memory bit with two states, the magnetic cell formed on the substrate and comprising: a multilayered free ferromagnetic stack having a net magnetization direction that is changeable between a first direction and a second substantially opposite direction such that the first and second substantially opposite directions correspond to the two states of the memory bit, the multilayered free ferromagnetic stack comprising first and second ferromagnetic layers and a non-magnetic spacer between the first and second ferromagnetic layers; a magnetic biasing layer in contact with and magnetically coupled to the multilayered free ferromagnetic stack to increase coercivity of the multilayered free ferromagnetic stack, the magnetic biasing layer configured such that the magnetization direction of the multilayered free ferromagnetic stack is changeable between the first direction and the second substantially opposite direction in response to a write electric current passing through the magnetic cell along a direction perpendicular to the first and second ferromagnetic layers to switch between the two states of the memory bit; a fixed ferromagnetic layer having a fixed magnetization direction, and an insulator barrier layer formed between the multilayered free ferromagnetic stack and fixed ferromagnetic layer to effectuate tunneling of electrons between the multilayered free ferromagnetic stack and fixed ferromagnetic layer under a bias voltage applied between the multilayered free ferromagnetic stack and fixed ferromagnetic layer and across the insulator barrier layer, wherein the multilayered free ferromagnetic stack is located between the magnetic biasing layer and the insulator barrier layer; and a circuit coupled to the magnetic cell, the circuit configured to perform a read operation and a write operation, wherein the circuit is configured such that in the read operation the circuit applies a read electric current passing perpendicularly through the magnetic cell that is insufficient to switch the magnetization direction of the multilayered free ferromagnetic stack, and wherein the circuit is configured such that in the write operation the circuit applies the write electric current greater than the read electric current to the magnetic cell sufficient to switch the magnetization direction of the multilayered free ferromagnetic stack based on spin transfer effect caused by the write electric current passing perpendicularly through the magnetic cell, and wherein the magnetic biasing layer is configured such that a switched magnetization direction of the multilayered free ferromagnetic stack is maintained after removal of the write electric current.