HIGH SPEED LOW POWER MAGNETIC DEVICES BASED ON CURRENT INDUCED SPIN-MOMENTUM TRANSFER

• US 20080259508A2
• Filed: 10/31/2007
• Published: 10/23/2008
• Est. Priority Date: 08/19/2003
• Status: Active Grant

• Current Assignee: New York University
• Original Assignee: New York University
• Inventors: Kent, Andrew, Ozyilmaz, Barbaros, Gonzalez Garcia, Enrique
• Granted Patent: US 7,573,737 B2
• Time in Patent Office: Days
• US Class Current: 360/324.11
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: G11C 11/1673 Reading or sensing circuits or methods
• CPC Class Codes: G11C 11/1675 Writing or programming circuits or methods
• CPC Class Codes: G11C 11/5607 using magnetic storage elements

Abstract

A high speed and low power method to control and switch the magnetization direction and/or helicity of a magnetic region in a magnetic device for memory cells using spin polarized electrical current. The magnetic device comprises a reference magnetic layer with a fixed magnetic helicity and/or magnetization direction and a free magnetic layer with a changeable magnetic helicity. The fixed magnetic layer and the free magnetic layer are preferably separated by a non-magnetic layer, and the reference layer includes an easy axis perpendicular to the reference layer. A current can be applied to the device to induce a torque that alters the magnetic state of the device so that it can act as a magnetic memory for writing information. The resistance, which depends on the magnetic state of the device, is measured to thereby read out the information stored in the device.

Claims

1. A magnetic device comprising:

a pinned magnetic layer with a magnetization vector having a fixed magnetization direction;

a free magnetic layer with at least one magnetization vector having a changeable magnetization direction;

a first non-magnetic layer spatially separating said free magnetic layer and said pinned magnetic layer;

a read-out magnetic layer with a magnetization vector having a fixed magnetization direction; and

a second non-magnetic layer spatially separating said free magnetic layer and said read-out magnetic layer, wherein the second non-magnetic layer includes an insulator.

2. The magnetic device according to claim 1, wherein the second non-magnetic layer includes an insulator which is sufficiently thin such that electrons may traverse the insulator by quantum mechanical tunneling.

3. The magnetic device according to claim 1 wherein the second non-magnetic layer includes an insulator including one or more of magnesium oxide, MgO, aluminum oxide, AlO or silicon oxide SiO, the proportion of oxygen to the first element need not be in the ratio of one to one.

4. The magnetic device according to claim 1 wherein the second non-magnetic layer includes an insulator including magnesium oxide, MgO that has an epitaxial lattice arrangement with at least one of the magnetic layers, either the reference layer or the free magnetic layer.

5. A magnetic device comprising:

a pinned magnetic layer with a magnetization vector having a fixed magnetization direction;

a free magnetic layer with at least one magnetization vector having a changeable magnetization direction;

a first non-magnetic layer spatially separating said free magnetic layer and said pinned magnetic layer;

wherein the first non-magnetic layer includes an insulator.

6. The magnetic device according to claim 5, wherein the first non-magnetic layer includes an insulator which is sufficiently thin such that electrons may traverse the insulator by quantum mechanical tunneling.

7. The magnetic device according to claim 5 wherein the first non-magnetic layer includes an insulator including one or more of magnesium oxide, MgO, aluminum oxide, AlO or silicon oxide SiO, the proportion of oxygen to the first element need not be in the ratio of one to one.

8. The magnetic device according to claim 5 wherein the first non-magnetic layer includes an insulator including magnesium oxide, MgO that has an epitaxial lattice arrangement with at least one of the magnetic layers, either the reference layer or the free magnetic layer.

9. A magnetic device comprising:

a pinned magnetic layer with a magnetization vector having a fixed magnetization direction;

a free magnetic layer with at least one magnetization vector having a changeable magnetization direction;

a first non-magnetic layer spatially separating said free magnetic layer and said pinned magnetic layer; and

wherein said pinned magnetic layer has a perpendicular component to the magnetic anisotropy.

10. The magnetic device of claim 9, wherein said pinned magnetic layer has a perpendicular component to the magnetic anisotropy that is sufficient to orient that magnetization perpendicular to the layer.

11. The magnetic device according to claim 9 wherein said pinned magnetic layer has a perpendicular component to the magnetic anisotropy and includes one or more of alloys of Fe and Pt, Fe and Pd, Co and Pt, Co and Pd, Co and Ni, Co and Au.

12. The magnetic device according to claim 9 wherein said pinned magnetic layer has a perpendicular component to the magnetic anisotropy achieved through the interfaces between dissimilar materials.

13. The magnetic device according to claim 12 where the interfaces are between different magnetic materials comprising Co, Ni or Fe or alloys of these elements.

14. The magnetic device according to claim 13 where the interfaces are between magnetic and non-magnetic materials, with the magnetic material including one or more of Co, Ni and Fe, an alloy of Co and Ni, an alloy of Co and Fe, an alloy of Ni and Fe, and the magnetic materials including one or more of Cu, Pt, Pd and Au.

15. A magnetic device comprising:

a pinned magnetic layer with a magnetization vector having a fixed magnetization direction;

a free magnetic layer with at least one magnetization vector having a changeable magnetization direction;

a first non-magnetic layer spatially separating said free magnetic layer and said pinned magnetic layer; and

wherein said free layer comprises one or more of Co, Ni and Fe and alloys of these elements, that are further alloyed with a non-magnetic element.

16. A magnetic device comprising:

a pinned magnetic layer with a magnetization vector having a fixed magnetization direction;

a free magnetic layer with at least one magnetization vector having a changeable magnetization direction;

a first non-magnetic layer spatially separating said free magnetic layer and said pinned magnetic layer; and

wherein said free layer comprises one or more of Co, Ni and Fe and is alloyed with Ti, V, Cr, Mn or Cu.

17. A magnetic device comprising:

a pinned magnetic layer with a magnetization vector having a fixed magnetization direction;

a free magnetic layer with at least one magnetization vector having a changeable magnetization direction;

a first non-magnetic layer spatially separating said free magnetic layer and said pinned magnetic layer; and

wherein said free layer comprises one or more of Co, Ni and Fe and alloys of these elements, that are further alloyed with an element which increases magnetization damping.

18. A magnetic device comprising:

a pinned magnetic layer with a magnetization vector having a fixed magnetization direction;

a free magnetic layer with at least one magnetization vector having a changeable magnetization direction;

a first non-magnetic layer spatially separating said free magnetic layer and said pinned magnetic layer; and

wherein said free layer is doped with one or more of Pd or Pt.

19. A magnetic device comprising:

a pinned magnetic layer with a magnetization vector having a fixed magnetization direction;

a free magnetic layer with at least one magnetization vector having a changeable magnetization direction;

a first non-magnetic layer spatially separating said free magnetic layer and said pinned magnetic layer; and

wherein said free layer is doped with rare earth atoms.