Spin-transfer switching magnetic elements using ferrimagnets and magnetic memories using the magnetic elements

1. A magnetic element comprising:

a pinned layer;

a spacer layer;

a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth transition metal alloy, a half-metallic ferrimagnet, and a bilayer including a rare earth transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer;

wherein the magnetic element is configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element;

wherein the pinned layer is a synthetic pinned layer including a first ferromagnetic layer, a second ferromagnetic layer, and a nonmagnetic conductive layer residing between the first ferromagnetic layer and the second ferromagnetic layer.

2. The magnetic element of claim 1 wherein the first ferromagnetic layer and the second ferromagnetic layer include at least one of Co, Ni, and Fe.

3. The magnetic element of claim 2 wherein the first ferromagnetic layer and the second ferromagnetic layer include at least one of B, Ta and Zr.

4. The magnetic element of claim 1 wherein the free layer includes the rare-earth transition metal alloy layer including CoRE x , where RE includes at least one of Gd, Tb, Dy, Ho, Em, and Tm, and x is at least six and not more than thirty percent.

5. The magnetic element of claim 1 wherein the free layer includes the rare-earth transition metal alloy layer including (CoRE x )Z y , where RE includes at least one of Gd, Tb, Dy, Ho, Em, and Tm, Z includes at least one of Au, Cu, B, Cr, and Mo, y is at least five and not more than forty percent, and x is at least ten and not more than thirty percent.

6. The magnetic element of claim 1 wherein the free layer includes the conductive ferrite, and wherein the conductive ferrite includes Fe 3 O 4 .

7. The magnetic element of claim 1 wherein the free layer includes the garnet and the garnet includes Yttrium Iron Garnet.

8. The magnetic element of claim 1 wherein the free layer includes the ferrimagnetic alloy, the ferrimagnetic alloy including at least of Mn 2 Sb, Mn 2 Sn, Mn 3 Ga, Mn 3 Ge 2 , Mn 3 In, FeGe 2 , FeSe, Cr 3 As 2 , and CrPt 3 .

9. The magnetic element of claim 1 wherein the free layer includes the heavy rare-earth-transition metal alloy, the heavy rare-earth-transition metal alloy including RCo 5 where R includes at least one of Gd, Tb, Dy, Ho, Eb, and Tm.

10. The magnetic element of claim 1 wherein the free layer includes the half-metallic ferrimagnet and wherein the half metallic ferrimagnet includes at least one of Co 2 (Cr 1-x Fe x )Al, Co 2 MnAl, and Co 2 MnSi.

11. The magnetic element of claim 1 wherein the spin current enhancement layer includes at least one of Co, Ni and Fe.

12. The magnetic element of claim 11 wherein the spin current enhancement layer includes at least one of B, Ta, and Zr.

13. The magnetic element of claim 1 wherein the free layer includes the bilayer including the rare earth transition metal alloy layer and the spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer.

14. The magnetic element of claim 1 wherein the rare-earth transition metal alloy layer includes at least one of CoRE w and (CoRE x )Z y , where RE includes at least one of Gd, Tb, Dy, Ho, Em, and Tm, Z includes at least one of Au, Cu, B, Cr, and Mo, w is at least six and not more than thirty percent, x is at least ten and not more than thirty percent, and y is at least five and not more than forty percent, and wherein the half metallic ferrimagnet includes at least one of Co 2 (Cr 1-x Fe x )Al, Co 2 MnAl, and Co 2 MnSi.

15. A magnetic element comprising:

a pinned layer;

a spacer layer;

a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth transition metal alloy, a half-metallic ferrimagnet, and a bilayer including a rare earth transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer;

wherein the magnetic element is configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element;

wherein the spacer layer is an insulating barrier layer and wherein the insulating barrier layer includes crystalline MgO.

16. The magnetic element of claim 15 wherein the insulating barrier layer has a thickness of less than three nanometers.

17. A magnetic element comprising:

a pinned layer;

a spacer layer;

a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth transition metal alloy, a half-metallic ferrimagnet, and a bilayer including a rare earth transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer;

wherein the magnetic element is configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element;

wherein the free layer has a saturation magnetization of not more than six hundred emu per cubic centimeter.

18. A magnetic element comprising:

a pinned layer;

a spacer layer;

a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth transition metal alloy, a half-metallic ferrimagnet, and a bilayer including a rare earth transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer;

an additional spacer layer; and

an additional pinned layer, the additional spacer layer residing between the free layer and the pinned layer;

wherein the magnetic element is configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element; and

wherein the free layer includes the rare-earth transition metal alloy layer and wherein the free layer further includes

an additional spin current enhancement layer residing between the rare earth-transition metal alloy layer and the additional spacer layer.

19. A magnetic element comprising:

a pinned layer;

a spacer layer;

a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth transition metal alloy, a half-metallic ferrimagnet, and a bilayer including a rare earth transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer;

an additional spacer layer; and

an additional pinned layer, the additional spacer layer residing between the free layer and the pinned layer;

wherein the magnetic element is configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element; and

wherein the additional pinned layer is a synthetic pinned layer including a first ferromagnetic layer, a second ferromagnetic layer, and a nonmagnetic conductive spacer layer residing between the first ferromagnetic layer and the second ferromagnetic layer.

20. The magnetic element of claim 19 wherein the pinned layer is a synthetic pinned layer and the additional pinned layer further includes a third ferromagnetic layer and an additional conductive spacer layer residing between the second ferromagnetic layer and the third ferromagnetic layer.

21. A magnetic element comprising:

a pinned layer;

a spacer layer;

a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth transition metal alloy, a half-metallic ferrimagnet, and a bilayer including a rare earth transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer;

an additional spacer layer;

an additional pinned layer, the additional spacer layer residing between the free layer and the pinned layer;

wherein the magnetic element is configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element; and

wherein the at least one of the spacer layer and the additional spacer layer is an insulating barrier layer including at least one of crystalline MgO and alumina.

22. A magnetic element comprising:

a pinned layer;

a spacer layer;

a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth transition metal alloy, a half-metallic ferrimagnet, and a bilayer including a rare earth transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer;

an additional spacer layer; and

an additional pinned layer, the additional spacer layer residing between the free layer and the pinned layer;

wherein the magnetic element is configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element

wherein the free layer includes the rare earth-transition metal alloy layer and the spin current enhancement layer; and wherein the free layer further includes:

an insertion layer between the rare earth-transition metal alloy layer and the spin current enhancement layer, the insertion layer including at least one of Ru, Rh, Ta, and Cr and having a thickness of not more than one nanometer.

23. A magnetic element comprising:

a pinned layer;

a barrier layer including at least one of alumina and crystalline MgO;

a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare earth-transition metal alloy, a half-metallic ferrimagnetic, and a bilayer including a rare earth-transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer, the rare earth-transition metal alloy layer including at least one of CoRE x and (CoRE j )Z k , where RE includes at least one of Gd, Tb, Dy, Ho, Em, and Tm and x is at least six and not more than thirty percent or (CoRE j )Z k , Z includes at least one of Au, Cu, B, Cr, and Mo, k is at least five and not more than forty percent, and j is at least ten and not more than thirty percent, the spin current enhancement layer including an alloy including at least one of Co, Ni, and Fe, the ferrimagnetic alloy including at least one of Mn 2 Sb, Mn 2 Sn, Mn 3 Ga, Mn 3 Ge 2 , Mn 3 In, FeGe 2 , FeSe, Cr 3 As 2 , and CrPt 3 , the heavy rare-earth-transition metal alloy including RCo 5 where R includes at least one of Gd, Tb, Dy, Ho, Eb, and Tm, the garnet includes Yttrium Iron Garnet, the conductive ferrite includes Fe 3 O 4 , the half-metallic ferrimagnet including at least one of Co 2 (Cr 1-x Fe x )Al, Co 2 MnAl, or Co 2 MnSi, the free layer having a saturation magnetization of not more than six hundred emu per cubic centimeter;

wherein the magnetic element is configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element.

24. The magnetic element of claim 23 further comprising:

an additional spacer layer; and

an additional pinned layer, the additional spacer layer residing between the free layer and the pinned layer.

25. The magnetic element of claim 24 wherein the at least one of the spacer layer and the additional spacer layer is an insulating barrier layer including at least one of crystalline MgO and alumina.

26. The magnetic element of claim 24 wherein the free layer includes the rare-earth transition metal alloy layer and wherein the free layer further includes:

an additional spin current enhancement layer residing between the rare earth transition metal alloy layer and the additional spacer layer.

27. The magnetic element of claim 23 wherein the free layer further has lateral dimensions not more than two hundred nanometers.

28. The magnetic element of claim 23 wherein the free layer includes the bilayer including the rare earth transition metal alloy layer and the spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer.

29. A magnetic memory comprising:

a plurality of magnetic elements, each of the plurality of magnetic elements including a pinned layer, a spacer layer, and a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth-transition metal alloy, a half-metallic ferrimagnet, and a bilayer including a rare earth-transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer, each of the plurality of the magnetic elements being configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element;

wherein the spacer layer includes at least one of a barrier layer, a conductor and a nano-oxide layer; and

wherein the free layer further has lateral dimensions not more than two hundred nanometers.

30. A magnetic memory comprising:

a plurality of magnetic elements, each of the plurality of magnetic elements including a pinned layer, a spacer layer, and a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth-transition metal alloy, a half-metallic ferrimagnet, and a bilayer including a rare earth-transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer, each of the plurality of the magnetic elements being configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element;

wherein the spacer layer includes at least one of a barrier layer, a conductor and a nano-oxide layer; and

wherein the free layer includes the bilayer including the rare earth transition metal alloy layer and the spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer.

31. A magnetic memory comprising:

a plurality of magnetic elements, each of the plurality of magnetic elements including a pinned layer, a barrier layer including at least one of alumina and crystalline MgO, and a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth-transition metal alloy, a half-metallic ferrimagnet and a bilayer including a rare earth-transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer, the rare earth-transition metal alloy layer including at least one of CoRE x and (CoRE j )Z k , where RE includes at least one of Gd, Tb, Dy, Ho, Em, and Tm and x is at least six and not more than thirty percent, k is at least five and not more than forty percent, and j is at least ten and not more than thirty percent, the ferrimagnetic alloy including at least one of Mn 2 Sb, Mn 2 Sn, Mn 3 Ga, Mn 3 Ge 2 , Mn 3 In, FeGe 2 , FeSe, Cr 3 As 2 , and CrPt 3 , the heavy rare-earth-transition metal alloy including RCo 5 where R includes at least one of Gd, Tb, Dy, Ho, Eb, and Tm, the garnet includes Yttrium Iron Garnet, the conductive ferrite includes Fe 3 O 4 , the half metallic ferrimagnet includes at least one of Co 2 (Cr 1-x Fe x ,)Al, Co 2 MnAl, and Co 2 MnSi, each of the plurality of the magnetic elements being configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element;

wherein the free layer further has lateral dimensions not more than two hundred nanometers.

32. A magnetic memory comprising:

a plurality of magnetic elements, each of the plurality of magnetic elements including a pinned layer, a barrier layer including at least one of alumina and crystalline MgO, and a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth-transition metal alloy, a half-metallic ferrimagnet and a bilayer including a rare earth-transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer, the rare earth-transition metal alloy layer including at least one of CoRE x and (CoRE j )Z k , where RE includes at least one of Gd, Tb, Dy, Ho, Em, and Tm and x is at least six and not more than thirty percent, k is at least five and not more than forty percent, and j is at least ten and not more than thirty percent, the ferrimagnetic alloy including at least one of Mn 2 Sb, Mn 2 Sn, Mn 3 Ga, Mn 3 Ge 2 , Mn 3 In, FeGe 2 , FeSe, Cr 3 As 2 , and CrPt 3 , the heavy rare-earth-transition metal alloy including RCo 5 where R includes at least one of Gd, Tb, Dy, Ho, Eb, and Tm, the garnet includes Yttrium Iron Garnet the conductive ferrite includes Fe 3 O 4 , the half metallic ferrimagnet includes at least one of Co 2 (Cr 1-x Fe x ,)Al, Co 2 MnAl, and Co 2 MnSi, each of the plurality of the magnetic elements being configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element; and

wherein the free layer includes the bilayer including the rare earth transition metal alloy layer and the spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer.

33. A magnetic memory comprising:

a plurality of magnetic elements, each of the plurality of magnetic elements including a pinned layer, a spacer layer, and a free layer, the free layer being ferrimagnetic and including at least one of a conductive ferrite, a garnet, a ferrimagnetic alloy excluding a rare earth, a heavy rare-earth-transition metal alloy, a half-metallic ferrimagnet, and a bilayer including a rare earth-transition metal alloy layer and a spin current enhancement layer residing between the rare-earth transition metal alloy layer and the spacer layer, each of the plurality of the magnetic elements being configured to allow the free layer to be switched using spin transfer when a write current is passed through the magnetic element; wherein the spacer layer includes at least one of a barrier layer, a conductor and a nano-oxide layer; and

wherein the rare-earth transition metal alloy layer includes at least one of CoRE w and (CoRE x )Z y , where RE includes at least one of Gd, Tb, Dy, Ho, Em, and Tm, Z includes at least one of Au, Cu, B, Cr, and Mo, w is at least six and not more than thirty percent, x is at least ten and not more than thirty percent, and y is at least five and not more than forty percent, and wherein the half metallic ferrimagnet includes at least one of Co 2 (Cr 1-x Fe x )Al, Co 2 MnAl, and Co 2 MnSi.