Magnetoresistive stack and method of fabricating same
A magnetoresistive element (e.g., a spin-torque magnetoresistive memory element) includes a fixed magnetic layer, a free magnetic layer, having a high-iron alloy interface region located along a surface of the free magnetic layer, wherein the high-iron alloy interface region has at least 50% iron by atomic composition, and a first dielectric, disposed between the fixed magnetic layer and the free magnetic layer. The magnetoresistive element further includes a second dielectric, having a first surface that is in contact with the surface of the free magnetic layer, and an electrode, disposed between the second dielectric and a conductor. The electrode includes: (i) a non-ferromagnetic portion having a surface that is in contact with a second surface of the second dielectric, and (ii) a second portion having at least one ferromagnetic material disposed between the non-ferromagnetic portion of the electrode and the conductor.
1. A magnetoresistive device, comprising:
a free magnetic layer having a first side and a second side;
a first electrode positioned on the first side of the free magnetic layer;
a second electrode positioned on the second side of the free magnetic layer;
a first dielectric layer in contact with the first electrode and the first side of the free magnetic layer; and
a second dielectric layer in contact with the second electrode and the second side of the free magnetic layer;
wherein an interface region of the free magnetic region on the second side has a higher iron content than an interface region of the free magnetic layer on the first side.
2. The device of claim 1 , wherein the interface region of the free magnetic layer on the second side has an iron content of greater than 20 percent by atomic composition, and the interface region of the free magnetic layer on the first side has an iron content of less than 20 percent by atomic composition.
3. The device of claim 1 , wherein the interface region of the free magnetic layer on the second side has an iron content of greater than 20 percent by atomic composition, and the interface region of the free magnetic layer on the first side has an iron content of approximately five percent by atomic composition.
4. The device of claim 1 , wherein the interface region of the free magnetic layer on the second side has an iron content of greater than 50 percent by atomic composition.
5. The device of claim 1 , wherein the interface region of the free magnetic layer on the second side has an iron content of greater than 20 percent by atomic composition and a boron content of between 14 percent and 20 percent by atomic composition, and the interface region of the free magnetic layer on the first side has an iron content of less than 20 percent by atomic composition and a boron content of greater than 20 percent by atomic composition.
6. The device of claim 1 , wherein the interface region of the free magnetic layer on the second side has an iron content of greater than 20 percent by atomic composition and a boron content of between 14 percent and 20 percent by atomic composition, and the interface region of the free magnetic layer on the first side has an iron content of 5 percent by atomic composition and a boron content of 25 percent by atomic composition.
7. The device of claim 1 , wherein at least one of the first electrode and the second electrode is a fixed magnetic layer.
8. The device of claim 1 , wherein the first electrode is a first fixed magnetic layer and the second electrode is a second fixed magnetic layer.
9. The device of claim 8 , wherein at least one of the first fixed magnetic layer and the second fixed magnetic layer includes a synthetic antiferromagnetic structure.
10. The device of claim 8 , wherein both the first fixed magnetic layer and the second fixed magnetic layer include a synthetic antiferromagnetic structure.
11. The device of claim 1 , wherein the first dielectric layer and the second dielectric layer include magnesium oxide (MgO).
12. The device of claim 1 , wherein the free magnetic layer includes two ferromagnetic layers coupled together by a layer of a non-ferromagnetic transition metal.
13. A magnetoresistive device, comprising:
a free magnetic layer including a first surface and a second surface, wherein a region of the free magnetic layer that includes the second surface has a higher iron content than a region of the free magnetic layer that includes the first surface;
a first fixed magnetic layer positioned on one side of the free magnetic layer;
a second fixed magnetic layer positioned on an opposite side of the free magnetic layer;
a first intermediate layer in contact with the first fixed magnetic layer and the first surface of the free magnetic layer; and
a second intermediate layer in contact with the second fixed magnetic layer and the second surface of the free magnetic layer.
14. The device of claim 13 , wherein the region of the free magnetic layer that includes the second surface has an iron content of greater than 20 percent by atomic composition, and the region of the free magnetic layer that includes the first surface has an iron content of less than 20 percent by atomic composition.
15. The device of claim 13 , wherein the region of the free magnetic layer that includes the second surface has an iron content of greater than 20 percent by atomic composition, and the region of the free magnetic layer that includes the first surface has an iron content of approximately five percent by atomic composition.
16. The device of claim 13 , wherein the region of the free magnetic layer that includes the second surface has an iron content of greater than 50 percent by atomic composition.
17. The device of claim 13 , wherein the region of the free magnetic layer that includes the second surface has an iron content of greater than 20 percent by atomic composition and a boron content of between 14 percent and 20 percent by atomic composition, and the region of the free magnetic layer that includes the first surface has an iron content of less than 20 percent by atomic composition and a boron content of greater than 20 by atomic composition.
18. The device of claim 13 , wherein the region of the free magnetic layer that includes the second surface has an iron content of greater than 20 percent by atomic composition and a boron content of between 14 percent and 20 percent by atomic composition, and the region of the free magnetic layer that includes the first surface has an iron content of 5 percent by atomic composition and a boron content of 25 percent by atomic composition.
19. The device of claim 13 , wherein at least one of the first fixed magnetic layer and the second fixed magnetic layer includes a synthetic antiferromagnetic structure.
20. The device of claim 13 , wherein each of the first fixed magnetic layer and the second fixed magnetic layer includes a synthetic antiferromagnetic structure.