Data storage in synthetic antiferromagnets included in magnetic tunnel junctions
AssigneeEverspin Technologies, Inc.
InventorsHan-Jong Chia, Sumio Ikegawa, Michael Tran, Jon Slaughter
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Abstract
A magnetoresistive memory device that stores data in the synthetic antiferromagnet (SAF) included in each spin-torque memory cell provides for more robust data storage. In normal operation, the memory cells use the free portion of the memory cell for data storage. Techniques for storing data in the reference portions of memory cells are presented, where an unbalanced SAF that includes ferromagnetic layers having different magnetic moments is used to lower the switching barrier for the SAF and allow for writing data values to the SAF using lower currents and magnetic fields than would be required for a balanced SAF.
Claims20
A magnetoresistive device, comprising:
- a free layer;
- a synthetic antiferromagnetic (SAF) reference layer that includes:
- a first ferromagnetic layer having a first magnetic moment;
- a second ferromagnetic layer having a second magnetic moment different than the first magnetic moment of the first ferromagnetic layer;
- and
- an antiferromagnetic coupling layer between the first and second ferromagnetic layers, wherein the antiferromagnetic coupling layer provides antiferromagnetic coupling between the first and second ferromagnetic layers;
- and
- a dielectric layer between the SAF reference layer and the free layer, wherein a magnetic field produced by the first and second ferromagnetic layers is perceived as approximately zero by the free layer, wherein the first ferromagnetic layer is between the free layer and the second ferromagnetic layer, and wherein the SAF reference layer is configured to store ROM-like data.
A method for storing data in a magnetoresistive device comprising a free layer and an unbalanced synthetic antiferromagnet (SAF), wherein the data is stored in the unbalanced SAF, the method comprising:
- applying a non-saturating first magnetic field along an axis corresponding to an easy axis of the magnetoresistive device, wherein the easy axis corresponds to a direction of magnetic vectors of the unbalanced SAF in a relaxed state, wherein the unbalanced SAF includes:
- a first ferromagnetic layer having a first magnetic moment and a first magnetic vector;
- a second ferromagnetic layer having a second magnetic moment and a second magnetic vector, wherein the second magnetic moment is different than the first magnetic moment of the first ferromagnetic layer;
- and
- an antiferromagnetic coupling layer between the first and second ferromagnetic layers, wherein the antiferromagnetic coupling layer provides antiferromagnetic coupling between the first and second ferromagnetic layers such that in a non-saturated state the first magnetic vector is opposite the second magnetic vector;
- while applying the first magnetic field, applying a second magnetic field perpendicular to the first magnetic field, wherein the first magnetic field is stronger than the second magnetic field;
- and
- while applying the first and second magnetic fields, applying a current through the magnetoresistive device, wherein spin-torque resulting from the current being spin-polarized by the free layer forces the magnetic vectors in the unbalanced SAF to invert such each of the first and second magnetic vectors rotates 180 degrees.
An integrated circuit, comprising:
- a magnetic memory cell that includes a magnetic tunnel junction, wherein the magnetic tunnel junction includes:
- a free layer;
- a synthetic antiferromagnetic (SAF) reference layer that includes:
- a first ferromagnetic layer having a first magnetic moment;
- a second ferromagnetic layer having a second magnetic moment different than the first magnetic moment of the first ferromagnetic layer;
- and
- an antiferromagnetic coupling layer between the first and second ferromagnetic layers, wherein the antiferromagnetic coupling layer provides antiferromagnetic coupling between the first and second ferromagnetic layers;
- and
- a dielectric layer between the SAF reference layer and the free layer, wherein magnetic field produced by the first and second ferromagnetic layers is perceived as approximately zero by the free layer, and wherein the first ferromagnetic layer is between the free layer and the second ferromagnetic layer;
- a write driver selectively coupled to the magnetic memory cell, wherein the write driver provides a write current, wherein, in conjunction with at least one external magnetic field, the write current is used to store data in the SAF reference layer, and wherein, during normal operation, data is stored in the free layer of the magnetic memory cell using the write current.
Dependencies are inferred from the claim text.