High speed low power magnetic devices based on current induced spin-momentum transfer

• US 7,911,832 B2
• Filed: 06/24/2009
• Issued: 03/22/2011
• Est. Priority Date: 08/19/2003
• Status: Active Grant

• Current Assignee: New York University
• Original Assignee: New York University
• Inventors: Kent, Andrew, Beaujour, Jean-Marc, Stein, Daniel
• Primary Examiner(s): Hoang; Huan
• Assistant Examiner(s): Hidalgo; Fernando N
• Application Number:
  US12/490,588
• Publication Number:
  US 20090296462A1
• Time in Patent Office: 636 Days
• Field of Search: 365/171, 365/173, 365/170, 365/159
• US Class Current: 365/171
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• 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 and/or magnetization direction. The fixed magnetic layer and the free magnetic layer are preferably separated by a non-magnetic layer. The fixed and free magnetic layers may have magnetization directions at a substantially non-zero angle relative to the layer normal. 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 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 at a substantially non-zero angle relative to a normal of a plane of the pinned magnetic layer;

a free magnetic layer with at least one magnetization vector having a changeable magnetization direction, wherein the magnetization vector of the free magnetic layer has at least a first stable state and a second stable state, and wherein the first and second stable states both have magnetization directions that are one of;

perpendicular to a plane of the free magnetic layer, or

in a plane of the free magnetic layer; and

a nonmagnetic layer spatially separating the pinned magnetic layer and the free magnetic layer,

wherein application of a current pulse of sufficient amplitude and duration through the magnetic device switches the magnetization vector of the free magnetic layer between the first and second stable states.

2. The magnetic device of claim 1, wherein the nonmagnetic layer comprises an insulator which is sufficiently thin such that elections may traverse tile insulator by quantum mechanical tunneling.

3. The magnetic device of claim 1, wherein the nonmagnetic layer comprises a nonmagnetic conductor.

4. The magnetic device of claim 1, wherein the pinned magnetic layer is formed by deposition of high magnetic anisotropy materials on a substrate at a substantially non-zero angle relative to a normal of a plane of the substrate.

5. A magnetic device comprising:

a pinned magnetic layer with a magnetization vector having a fixed magnetization direction that is one of;

perpendicular to a plane of the pinned magnetic layer, or at a substantially non-zero angle relative to a normal of the plane of the pinned magnetic layer;

a free magnetic layer with at least one magnetization vector having a changeable magnetization direction, wherein the magnetization vector of the free magnetic layer has at least a first stable state and a second stable state, and wherein the first and second stable states each have magnetization directions that are at a substantially non-zero angle relative to a normal of a plane of the free magnetic layer; and

a nonmagnetic layer spatially separating the pinned magnetic layer and the free magnetic layer,

wherein application of a current pulse of sufficient amplitude and duration through the magnetic device switches the magnetization vector of the free magnetic layer between the first and second stable states.

6. The magnetic device of claim 5, wherein the nonmagnetic layer comprises an insulator which is sufficiently thin such that electrons may traverse the insulator by quantum mechanical tunneling.

7. The magnetic device of claim 5, wherein the nonmagnetic layer comprises a nonmagnetic metal.

8. The magnetic device of claim 5, wherein the pinned magnetic layer is formed by deposition of high magnetic anisotropy materials on a substrate at a substantially non-zero angle relative to a normal of a plane of the substrate.

9. A magnetic device comprising:

a substantially annular pinned magnetic layer having a fixed magnetic helicity and a magnetization vector having a magnetization direction at one of a substantially non-zero angle relative to a normal of a plane of the pinned magnetic layer or perpendicular to the plane of the pinned magnetic layer;

a substantially annular free magnetic layer having a changeable magnetic helicity, wherein the magnetic helicity of the free magnetic layer has at least a first stable state and a second stable state; and

a non-magnetic layer spatially separating the pinned magnetic layer and the free magnetic layer,

wherein the free magnetic layer has a radius that is approximately equal to a critical radius and application of a current pulse of sufficient amplitude and duration through the magnetic device switches the magnetic helicity of the free magnetic layer between the first and second stable states.

10. The magnetic device of claim 9, wherein the nonmagnetic layer comprises an insulator which is sufficiently thin such that electrons may traverse the insulator by quantum mechanical tunneling.

11. The magnetic device of claim 9, wherein the nonmagnetic layer comprises a nonmagnetic conductor.

12. The magnetic device of claim 9, wherein the pinned and free magnetic layers comprise at least one of permalloy, the Ll₀ phase of FePt, or Co, B, Ni, Pt, Fe or Pd or alloys thereof.

13. A memory array comprising:

at least one bit cell including;

a magnetic device having;

a substantially annular pinned magnetic layer having a fixed magnetic helicity and a magnetization vector having a magnetization direction at one of a substantially non-zero angle relative to a normal of a plane of the pinned magnetic layer or perpendicular to the plane of the pinned magnetic layer; and

;

a substantially annular free magnetic layer having a changeable magnetic helicity, wherein the magnetic helicity of the free magnetic layer has at least a first stable state and a second stable state; and

a non-magnetic layer spatially separating the pinned magnetic layer and the free magnetic layer,

wherein the free magnetic layer has a radius that is approximately equal to a critical radius and application of a current pulse of sufficient amplitude and duration through the magnetic device switches the magnetic helicity of the free magnetic layer between the first and second stable states; and

at least one transistor for current control and readout; and

a word line, wherein application of a voltage on the word line addresses and activates at least one bit cell.

14. The memory array of claim 13, wherein at least one transistor includes a CMOS transistor.