Magnetic memory devices
Magnetic memory devices are provided, the devices include at least memory cell and a reference cell on a substrate. The memory cells include a first base magnetic layer, a free layer, and a first tunnel barrier layer between the first base magnetic layer and free layer. The reference memory cell includes a second base magnetic layer, a reference magnetic layer, and a second tunnel barrier layer between the second base magnetic layer and reference magnetic layer. The reference magnetic layer has a magnetic direction substantially perpendicular to that of the free layer.
1. A magnetic memory device, comprising:
at least one memory cell and a reference cell provided on a substrate,
wherein the at least one memory cell includes a first base magnetic layer, a free layer, and a first tunnel barrier layer between the first base magnetic layer and the free layer,
the reference cell includes a second base magnetic layer, a reference magnetic layer, and a second tunnel barrier layer between the second base magnetic layer and the reference magnetic layer; and
the reference magnetic layer has a magnetization direction substantially perpendicular to a magnetization direction of the free layer.
2. The magnetic memory device of claim 1 , wherein the magnetization direction of the reference magnetic layer is fixed in a direction substantially perpendicular to a magnetization easy-axis of the free layer when a read current is applied to the reference cell.
3. The magnetic memory device of claim 1 , wherein the first and second base magnetic layers have a magnetization direction substantially parallel with top surfaces of the first and second tunnel barrier layers, and
the free layer has a magnetization direction which changes to a direction parallel or anti-parallel with magnetization directions of the first and second base magnetic layers.
4. The magnetic memory device of claim 3 , wherein the reference magnetic layer has a magnetization direction substantially perpendicular to the top surfaces of the first and second tunnel barrier layers.
5. The magnetic memory device of claim 3 , wherein the reference magnetic layer includes the same material as the free layer, and is thinner than the free layer.
6. The magnetic memory device of claim 3 , wherein the reference cell includes a non-magnetic metal oxide layer in contact with the reference magnetic layer.
7. The magnetic memory device of claim 6 , wherein the reference magnetic layer and the free layer have the substantially same thickness.
8. The magnetic memory device of claim 6 , wherein the non-magnetic metal oxide layer includes a nano-oxide layer having a thickness less than the second tunnel barrier layer.
9. The magnetic memory device of claim 6 , wherein the reference magnetic layer is provided below the second base magnetic layer,
the reference cell includes a seed layer below the reference magnetic layer, and
the non-magnetic metal oxide layer is provided between the seed layer and reference magnetic layer.
10. The magnetic memory device of claim 1 , wherein the first and second base magnetic layers have magnetization directions substantially perpendicular to top surfaces of the first and second tunnel barrier layers, and
the free layer has a magnetization direction which changes to a direction parallel or anti-parallel with magnetization directions of the first and second base magnetic layers.
11. The magnetic memory device of claim 10 , wherein the reference magnetic layer has a magnetization direction substantially parallel to the top surfaces of the first and second tunnel barrier layers.
12. The magnetic memory device of claim 10 , wherein the reference magnetic layer is thicker than the free layer.
13. The magnetic memory device of claim 10 , wherein the at least one memory cell includes a non-magnetic metal oxide layer in contact with the free layer.
14. The magnetic memory device of claim 1 , wherein the reference cell is disposed on the at least one memory cell.