Electronic devices based on current induced magnetization dynamics in single magnetic layers

• US 7,986,544 B2
• Filed: 11/05/2007
• Issued: 07/26/2011
• Est. Priority Date: 11/03/2006
• Status: Active Grant

• Current Assignee: New York University
• Original Assignee: New York University
• Inventors: Özyilmaz, Barbaros, Kent, Andrew
• Primary Examiner(s): AUDUONG, GENE NGHIA
• Application Number:
  US11/935,392
• Publication Number:
  US 20110038198A1
• Time in Patent Office: 1,359 Days
• Field of Search: 365/148, 365/158, 365/163, 365/171
• US Class Current: 365/148
• 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: H01F 1/404 of III-V type, e.g. In1-x Mnx As
• CPC Class Codes: H01F 10/193 Magnetic semiconductor compounds in general H01F1/40; multilayers, e.g. superlattices H01F10/3213
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

The present invention generally relates to magnetic devices used in memory and information processing applications, such as giant magneto-resistance (GMR) devices and tunneling magneto-resistance devices. More specifically, the present invention is directed to a single ferromagnetic layer device in which an electrical current is used to control and change magnetic configurations as well as induce high frequency magnetization dynamics. The magnetic layer includes full spin-polarized magnetic material, which may also have non-uniform magnetization. The non-uniform magnetization is achieved by varying the shape or roughness of the magnetic material. The present invention may be used in memory cells, as well as high frequency electronics, such as compact microwave sources, detectors, mixers and phase shifters.

Claims

1. A magnetic device capable of current induced single layer magnetic configuration switching, comprising:

a nanopillar structure having a single magnetic layer including a nonuniform magnetization material which when traversed by a spin polarized current of a first polarity exhibits a second electrical resistance value which is different from a first electrical resistance value exhibited by said magnetic layer prior to being traversed by said current, wherein a change between said first electrical resistance value and an associated magnetization configuration and said second electrical resistance value with an associated switched second magnetization configuration exhibits hysteretic characteristics.

2. The magnetic device of claim 1, wherein said magnetic layer is positioned asymmetrically within said nanopillar structure.

3. The magnetic device of claim 1, wherein said nonuniform magnetization material is formed using a preselected shape which imparts a nonuniform magnetization.

4. The magnetic device of claim 1, wherein said nonuniform magnetization material includes a magnetization layer grown over a roughened portion.

5. The magnetic device of claim 1, wherein said nonuniform magnetization material includes a roughened portion formed lithographically.

6. The magnetic device of claim 1, wherein said nonuniform magnetization material includes a granular solid.

7. The magnetic device of claim 6, wherein the granular solid includes a magnetic material and a non-magnetic material.

8. The magnetic device of claim 7, wherein the magnetic material includes a transition metal selected from the group consisting of Ni, Fe, Co and alloys thereof, and the non-magnetic material is selected from the group consisting of Au, Ag, Cu, Cr, Rh and alloys thereof.

9. The magnetic device of claim 1, wherein said nanopillar comprises a layer of Pt, followed by a first layer of Cu, followed by a layer of Co, followed by a second layer of Cu.

10. The magnetic device of claim 1, wherein said magnetic material is selected from the group consisting of Fe₃O₄, CrO₂, Manganite materials including LaCaMnO₃, La_1-xCa_xMnO₃, La_0.7Ca_0.3MnO₃, LSMO materials including La_1-xSr_xMnO₃, La_0.7Sr_0.3 MnO₃ and Heusler alloys.

11. The magnetic device of claim 1, wherein said magnetic material includes one of a low magnetization density ferromagnetic material and a dilute ferromagnetic semiconductor, wherein the low magnetization density ferromagnetic material is selected from the group consisting of Co, Ni, Fe alloyed with Ti, V, Cr, Mn or Cu.

12. A magnetic memory device capable of current induced single layer magnetic configuration switching, comprising:

a nanopillar structure having a single magnetic layer including a nonuniform magnetization material of a first magnetization configuration which when traversed by a spin polarized current of a first polarity changes to a second magnetization configuration and exhibits a second electrical resistance value which is different from a first electrical resistance value exhibited by said magnetic layer prior to being traversed by said current, wherein the presence of one of said first electrical resistance value and said second electrical resistance value indicates an information element stored in said magnetic memory device, and wherein a change between said first electrical resistance value and said second electrical resistance value exhibits hysteretic characteristics.

13. The magnetic memory device of claim 12 wherein said magnetic layer is positioned asymmetrically within said nanopillar structure.

14. The magnetic memory device of claim 12, wherein said nonuniform magnetization material includes a magnetization layer grown over a roughened portion.

15. The magnetic memory device of claim 12, wherein said nonuniform magnetization material includes one of a roughened portion formed lithographically and a granular solid.

16. The magnetic memory device of claim 12, wherein said nanopillar comprises a layer of Pt, followed by a first layer of Cu, followed by a layer of Co, followed by a second layer of Cu.

17. The magnetic memory device of claim 12, wherein said magnetic material is selected from the group consisting of Fe₃O₄, CrO₂, Manganite materials including LaCaMnO₃, La_1-xCa_xMnO₃, La_0.7Ca_0.3MnO₃, LSMO materials including La_1-xSr_xMnO₃, La_0.7Sr_0.3MnO₃ and Heusler alloys.

18. The magnetic memory device of claim 12, wherein said magnetic material includes one of a low magnetization density ferromagnet and a dilute ferromagnetic semiconductor.

19. A magnetic material oscillator, comprising:

a single magnetic layer including a nonuniform magnetization material which when traversed by a spin polarized current of a predetermined current density range thereby results in a reorientation of the magnetic moments of the magnetic layer which takes place in a substantially oscillatory manner such that an electrical resistance value characteristic of said magnetic layer oscillates in a substantially regular manner.

20. The magnetic material oscillator of claim 19, further comprising an array of nanocontacts arranged to provide contact with said magnetic layer, wherein said array of contacts is one of a one-dimensional array and a two-dimensional array.

21. The magnetic material oscillator of claim 19, wherein said nonuniform magnetization material is selected from the group consisting of Fe₃O₄, CrO₂, Manganite materials including LaCaMnO₃, La_1-xCa_xMnO₃, La_0.7Ca_0.3MnO₃, LSMO materials including La_1-xSr_xMnO₃, La_0.7Sr_0.3MnO₃ and Heusler alloys, and wherein said magnetic material optionally includes one of a low magnetization density ferromagnet and a dilute ferromagnetic semiconductor.

22. The magnetic material oscillator of claim 19, wherein said predetermined current density range ranges from 10⁵ A/cm² to 10⁸ A/cm².

23. A magnetic material frequency mixer, comprising:

a single magnetic layer including a nonuniform magnetization material which when traversed by an oscillating spin polarized current of a predetermined current density range results in a reorientation of the magnetic moments of the magnetic layer which thereby takes place in a substantially oscillatory manner such that an electrical resistance value characteristic of said magnetic layer oscillates in a substantially regular manner, such that when a frequency of the oscillating spin polarized current is substantially equivalent to a frequency of the magnetic layer oscillation, an oscillating voltage will be developed by the magnetic layer, the oscillating voltage having a frequency which is the difference of the frequency of the oscillating spin polarized current and the frequency of the magnetic layer oscillation.

24. The magnetic material frequency mixer of claim 23, wherein the difference signal is a dc signal.

25. The magnetic material frequency mixer of claim 23, further comprising an input for receiving a dc current which is used to modify the frequency of the magnetic layer oscillation.