ST-RAM magnetic element configurations to reduce switching current
View Patent ↗In order to increase an efficiency of spin transfer and thereby reduce the required switching current, a current perpendicular to plane (CPP) magnetic element for a memory device includes either one or both of a free magnetic layer, which has an electronically reflective surface, and a permanent magnet layer, which has perpendicular anisotropy to bias the free magnetic layer.
1. A CPP magnetic element for a memory device, the magnetic element comprising:
a free magnetic layer separated from a reference magnetic layer by a non-magnetic spacer layer; and
a first permanent magnet layer separated from the free layer by a first exchange decoupling layer and located on a side of the free layer which is opposite the spacer layer, the first permanent magnet layer having perpendicular anisotropy for biasing the free layer, the first decoupling layer being insulative; and
a first electrode overlaying the first permanent magnet layer, extending sideways beyond a perimeter thereof, and alongside the first decoupling layer so as to be partially located on the side of the free layer which is opposite the spacer layer.
2. The element of claim 1 , wherein the first permanent magnet layer is a monolayer of a particular material.
3. The element of claim 1 , wherein the first permanent magnet layer comprises multiple layers of materials.
4. The element of claim 1 , wherein the spacer layer is conductive.
5. The element of claim 1 , wherein the spacer layer is insulative.
6. The element of claim 1 , wherein the spacer layer forms a current constrictive path.
7. The element of claim 1 , wherein the free magnetic layer has an electronically reflective surface, the reflective surface interfacing both with the first decoupling layer and the first electrode.
8. The element of claim 1 , further comprising a second permanent magnet layer separated from the reference layer by at least a second insulative exchange decoupling layer and having perpendicular anisotropy for further biasing the free layer, the second permanent magnet layer located on a side of the reference magnetic layer which is opposite the spacer layer.
9. The element of claim 8 , further comprising:
a first electrode overlaying the first permanent magnet layer, extending sideways beyond a perimeter thereof, and alongside the first decoupling layer so as to be located on the side of the free layer which is opposite the spacer layer; and
a second electrode overlaying the second permanent magnet layer, extending sideways beyond a perimeter thereof, and alongside the second decoupling layer so as to be located on the side of the reference layer which is opposite the spacer layer.
10. The element of claim 8 , further comprising:
a pinned layer overlaying a side of the reference magnetic layer, which side is opposite the spacer layer;
wherein the pinned layer is separated from the reference magnetic layer by a Ru layer having an electronically reflective surface.
11. The element of claim 10 , wherein the electronically reflective surface of the Ru layer interfaces with the reference magnetic layer.
12. A CPP magnetic element for a memory device, the magnetic element comprising:
a free magnetic layer separated from a reference magnetic layer by a non-magnetic spacer layer;
a first conductive layer overlaying a side of the free magnetic layer, which side is opposite the spacer layer; and
a second conductive layer overlaying a side of the reference magnetic layer, which side is opposite the spacer layer, the second conductive layer having an electronically reflective surface interfacing with the reference magnetic layer.
13. The element of claim 12 , wherein the free magnetic layer has an electronically reflective surface that interfaces with the first conductive layer.
14. The element of claim 13 , wherein the first and second conductive layers comprise electrodes.
15. The element of claim 13 , wherein the second conductive layer is an antiferromagnetic layer.
16. A CPP magnetic element for a memory device, the magnetic element comprising:
a free magnetic layer separated from a reference magnetic layer by a non-magnetic spacer layer; and
a first permanent magnet layer separated from the free layer by a first exchange decoupling layer and located on a side of the free layer which is opposite the spacer layer, the first permanent magnet layer having perpendicular anisotropy for biasing the free layer, a surface of the free magnetic layer being electronically reflective and interfacing with the first decoupling layer; and
a pinned layer overlaying a side of the reference magnetic layer, which side is opposite the spacer layer, the pinned layer separated from the reference magnetic layer by a Ru layer having an electronically reflective surface interfacing with the reference magnetic layer.
17. The element of claim 16 , further comprising a second permanent magnet layer separated from the reference layer and pinned layer by at least a second exchange decoupling layer and having perpendicular anisotropy for further biasing the free layer.
18. The element of claim 17 , wherein the first and second decoupling layers are insulative, and further comprising:
a first electrode overlaying the first permanent magnet layer, extending sideways beyond a perimeter thereof, and alongside the first decoupling layer so as to be located on the side of the free layer which is opposite the spacer layer; and
a second electrode overlaying the second permanent magnet layer, extending sideways beyond a perimeter thereof, and alongside the second decoupling layer so as to be located on the side of the reference layer which is opposite the spacer layer.