Memory with separate read and write paths
A memory unit includes a giant magnetoresistance cell electrically coupled between a write bit line and a write source line. The giant magnetoresistance cell includes a free magnetic layer separated from a first pinned magnetic layer by a first non-magnetic electrically conducting layer. A magnetic tunnel junction data cell is electrically coupled between a read bit line and a read source line. The magnetic tunnel junction data cell includes the free magnetic layer separated from a second pinned magnetic layer by an oxide barrier layer. A write current passes through the giant magnetoresistance cell to switche the giant magnetoresistance cell between a high resistance state and a low resistance state. The magnetic tunnel junction data cell is configured to switch between a high resistance state and a low resistance state by magnetostatic coupling with the giant magnetoresistance cell, and be read by a read current passing though the magnetic tunnel junction data cell.
1. A memory unit comprising:
a giant magnetoresistance cell electrically coupled between a write bit line and a write source line, a write current passing through the giant magnetoresistance cell switches the giant magnetoresistance cell between a high resistance state and a low resistance state; and
a magnetic tunnel junction data cell electrically coupled between a read bit line and a read source line, the magnetic tunnel junction data cell is configured to switch between a high resistance state and a low resistance state, and be read by a read current passing though the magnetic tunnel junction data cell;
a bridge of magnetic dots extend between the giant magnetoresistance cell and the magnetic tunnel junction data cell that provides magnetostatic coupling between the giant magnetoresistance cell and the magnetic tunnel junction data cell to switch the magnetic tunnel junction data cell between a high resistance state and a low resistance state.
2. A memory unit according to claim 1 , wherein the magnetic tunnel junction data cell comprises a free magnetic layer separated from a pinned magnetic layer by an oxide barrier layer and the giant magnetoresistance cell comprises a free magnetic layer separated from a pinned magnetic layer by a non-magnetic electrically conducting layer, and the free magnetic layer of the magnetic tunnel junction data cell is inplane with the free magnetic layer of the giant magnetoresistance cell, and the pinned magnetic layer of the magnetic tunnel junction data cell is not in plane with the pinned magnetic layer of the giant magnetoresistance cell.
3. A memory unit according to claim 1 , wherein the giant magnetoresistance cell is electrically connected to a write transistor and the write transistor is electrically connected to a write word line, and the magnetic tunnel junction data cell is electrically connected to a read transistor and the read transistor is electrically connected to a read word line.
4. A memory unit according to claim 1 , wherein the giant magnetoresistance cell has a first free magnetic layer volume and the magnetic tunnel junction data cell has a second free magnetic layer volume, and the second free magnetic layer volume is less than the first free magnetic layer volume.
5. A memory unit according to claim 1 , wherein the giant magnetoresistance cell and the magnetic tunnel junction data cell are separated from each other.
6. A memory unit according to claim 1 , wherein the bridge of magnetic dots comprises a plurality of the magnetic dots wherein at least selected magnetic dots have a diameter of about 100 nm and placed on a pitch of about 135 nm and having a thickness of about 10 nm.
7. A memory unit according to claim 1 , wherein the read bit line and write bit line are separately addressable and the read source line and write source line are separately addressable.
8. A memory array comprising two or more memory units according to claim 1 arranged and configured in an array.
9. A method comprising:
passing a write current thorough a giant magnetoresistance cell to switch a free magnetic layer of the giant magnetoresistance cell between a high resistance state and a low resistance state;
switching a free layer of a magnetic tunnel junction data cell between a high resistance state and a low resistance state by magnetostatic coupling with the free magnetic layer of the giant magnetoresistance cell via a bridge of magnetic dots disposed between the free layer of a magnetic tunnel junction data cell and the free magnetic layer of the giant magnetoresistance cell; and
reading the resistance state of the magnetic tunnel junction data cell by passing a reading current through the magnetic tunnel junction data cell.
10. A method according to claim 9 , wherein the write current has a write current path and the read current has a read current path and the write current path is different than the read current path.
11. A method according to claim 9 , wherein the write current does not pass through the magnetic tunnel junction data cell and the read current does not pass through the giant magnetoresistance cell.
12. A method according to claim 9 , wherein giant magnetoresistance cell is electrically isolated from the magnetic tunnel junction data cell.