Separate write and read access architecture for a magnetic tunnel junction
A magnetoresistive device is provided with separate read and write architecture. In one embodiment, a magnetic tunnel junction (MTJ) has a nonmagnetic nonconductive barrier layer sandwiched between two ferromagnetic conducting layers. A first read line is coupled to a first ferromagnetic layer and a second read line is coupled to a second ferromagnetic layer such that a voltage difference between the two read lines will produce a current flowing perpendicularly through each layer of the MTJ. A first write line is separated from the first read line by a first insulator and a second write line is separated from the second read line by a second insulator.
1. A magnetoresistive memory cell comprising:
a magnetic tunneling junction (MTJ) element having a first side and a second side, the MTJ element comprising a barrier layer sandwiched between a magnetic free layer and a magnetic pinned layer in which the magnetic pinned layer is thicker and has a greater coercivity than the magnetic free layer;
a first read line deposited on the first side;
a first write line separated from the first read line by a first insulator, the first insulator deposited on the first read line, and the first write line deposited on the first insulator;
a second read line coupled to the second side, the MTJ element grown on the second read line; and
a second write line separated from the second read line by a second insulator, the second read line being deposited on the second insulator.
2. The memory cell of claim 1 , wherein the second read line runs perpendicular to the first read line.
3. The memory cell of claim 1 , wherein the magnetic pinned layer comprises:
a magnetizable reference layer; and
an anti-ferromagnetic layer for pinning the magnetization direction of the magnetizable reference layer, wherein the magnetization direction of the magnetizable reference layer remains substantially fixed.
4. The memory cell of claim 1 ,
wherein the first write line runs perpendicular to the second write line, and
wherein the first read line runs parallel to the first write line, and
wherein the first read line runs parallel to the second write line.
5. The memory cell of claim 1 ,
wherein the first write line runs perpendicular to the second write line, and
wherein the first read line runs parallel to the second write line, and
wherein the second read line runs parallel to the first write line.
6. A magnetic random access memory (MRAM) comprising:
a matrix of magnetic tunnel junction (MTJ) cells arranged in a plurality of rows and a plurality of columns;
each MTJ cell having a first side and a second side, the magnetic tunnel junction comprising a tunnel barrier layer sandwiched between a storage layer and a pinned layer in which the magnetic pinned layer is thicker and has a greater coercivity than the magnetic free layer;
each row comprising:
a first read line coupled to the first side of each MTJ cell in the row; and
a second write line for applying an external magnetic field to the row;
each column comprising:
a second read line coupled to the second side of each MTJ cell in the columns
each MTJ cell grown on the second read line; and
a first write line for applying an external magnetic field to the column; and
wherein at each MTJ cell, the first write line is separated from the first read line by a first insulator and the second write line is separated from the second read line by a second insulator.
7. The MRAM of claim 6 , wherein:
the pinned layer is a conducting magnetic layer that serves as a magnetic reference;
the storage layer is a conducting magnetic layer that serves as data storage; and
the tunnel barrier layer is a non-magnetic insulating layer that is sandwiched between the pinned layer and the storage layer.
8. The MRAM of claim 7 ,
wherein the pinned layer comprises a NiFe alloy,
wherein the storage layer comprises a NiFe alloy, and
wherein the tunnel barrier comprises an aluminum oxide compound.