SPINTRONIC DEVICE WITH CONTROL BY DOMAIN WALL DISPLACEMENT INDUCED BY A CURRENT OF SPIN-POLARIZED CARRIERS

• US 20090273421A1
• Filed: 12/14/2005
• Published: 11/05/2009
• Est. Priority Date: 12/15/2004
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Fert, Albert, Nguyen Van Dau, Frederic, Munoz Sanchez, Manuel, Grollier, Julie, Cros, Vincent
• Granted Patent: US 7,969,762 B2
• Time in Patent Office: Days
• US Class Current: 335/302
• 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 11/1675 Writing or programming circuits or methods
• CPC Class Codes: G11C 19/0808 using magnetic domain propagation
• CPC Class Codes: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

The general field of the invention is that of spintronics, namely the field of electronics using the magnetic spin properties of electrons. The main fields of application are the very large-scale magnetic storage of information and the measurement of local magnetic fields. The object of the invention is to considerably reduce the energy needed to reverse the magnetic domains of the ferromagnetic elements of submicron dimensions using the mechanism of the domain wall displacements that is induced either by just a current of spin-polarized carriers or by the combination of a current of spin-polarized carriers and a magnetic field, at least one of these being variable. This domain wall displacement results in a change of magnetic polarization in a specified switching zone. Several devices according to the invention are described that possess from one switching zone up to a plurality of switching zones according to the invention.

Claims

1. A spintronic device, comprising:

at a first ferromagnetic structure including a first magnetic switching zone, said structure comprising at least one first magnetic domain in which the magnetic moments M are all aligned in a first direction and a second magnetic domain in which the magnetic moments are all aligned in a second direction different than the first direction, the first domain being separated from the second domain by a magnetic domain wall,

said structure including means for stabilizing said magnetic domain wall in two stable positions, the first switching zone being located between these two stable positions, said domain wall being able to move from the first stable position to the second stable position at least due to the effect of a first current of spin-polarized carriers passing through said structure, and said switching zone thus belonging either to the first magnetic domain or to the second magnetic domain; and

the device including a first magnetic element, the magnetic moments of said second magnetic element not being coupled with the magnetic moments of the first magnetic switching zone.

2. The spintronic device as claimed in claim 1, wherein at least one second magnetic element is placed between the first switching zone and the first magnetic element in such a way that the magnetic moments of said second element are coupled with the magnetic moments of said switching zone, whether said switching zone belongs to the first magnetic domain or to the second magnetic domain.

3. The spintronic device as claimed in claim 1, including at least one first separating layer placed between the first magnetic element and the first switching zone.

4. The spintronic device as claimed in claim 3, wherein the separating layer is made of a nonmagnetic material.

5. The spintronic device as claimed in claim 1, wherein the displacement is obtained by the combined effect of the first current and a magnetic field, the field lines of which pass through the magnetic switching zone so as to be approximately parallel to the direction of the first current, at least the first current or the magnetic field being variable.

6. The spintronic device as claimed in claim 5, including a conducting line placed beneath the magnetic switching zone and approximately perpendicular to the direction of the first current, a second current passing through said line so as to generate the magnetic field in the magnetic switching zone.

7. The spintronic device as claimed in claim 1, wherein the first current lies above a certain threshold value sufficient to cause displacement of the domain wall from the first stable position to the second stable position, said switching zone thus belonging either to the first magnetic domain or to the second magnetic domain.

8. The spintronic device as claimed in claim 7, including a second ferromagnetic structure comprising a second magnetic switching zone facing the first switching zone of the first ferromagnetic structure, said second structure including at least one third magnetic domain in which the magnetic moments are all aligned in a third direction and a fourth magnetic domain in which the magnetic moments are all aligned in a fourth direction different than the third direction, the third domain being separated from the fourth domain by a second magnetic domain wall, said second structure also including means for stabilizing said magnetic domain wall in third and fourth stable positions, the second switching zone lying between these two stable positions, it being possible for said second domain wall to move from the third stable position to the fourth stable position under the effect of a second spin-carrier current passing through said second structure, said second current being above a certain threshold value, the second switching zone thus belonging either to the third magnetic domain or to the fourth magnetic domain, said second switching zone of said second structure being separated from the first switching zone of the first ferromagnetic structure by at least one separating layer.

9. The spintronic device as claimed in claim 8, wherein each threshold current is between one thousand amps per square centimeter and one million amps per square centimeter.

10. The spintronic device as claimed in claim 8, wherein the first ferromagnetic structure or the second ferromagnetic structure are ferromagnetic strips, the widths of which are between a few nanometers and a few microns and the thicknesses of which are between a few nanometers and a few tens of nanometers.

11. The spintronic device as claimed in claim 10, wherein each ferromagnetic strip has, in each stable position, a local change of geometry.

12. The spintronic device as claimed in claim 11, wherein the local change of geometry is either a narrowing, or a thinning or a widening of the ferromagnetic strip.

13. The spintronic device as claimed in claim 12, wherein each ferromagnetic strip has, in each stable position, a local change of structure.

14. The spintronic device as claimed in claim 13, wherein the local change of structure is obtained by oxidation.

15. The spintronic device as claimed in claim 1, wherein the ferromagnetic structure comprises, beneath the switching zone, a combination of magnetic layers and nonmagnetic layers for concentrating the spin flux in the switching zone.

16. The spintronic device as claimed in claim 15, wherein the combination comprises at least two ferromagnetic blocks lying on either side of the switching zone and separated by a first nonmagnetic layer, the combination consisting of the two blocks and the nonmagnetic layer being isolated from the ferromagnetic structure by a second nonmagnetic layer.

17. The spintronic device as claimed in claim 16, wherein the ferromagnetic blocks have a width equivalent to that of the strip and a thickness greater than that of the strip, typically ten times the thickness of the strip.

18. The spintronic device as claimed in claim 16, wherein the magnetization directions of the two ferromagnetic blocks make a nonzero angle between them.

19. The spintronic device as claimed in claim 16, wherein the magnetization directions of the two ferromagnetic blocks make an angle of approximately 180 degrees between them, the magnetizations of the two blocks thus being antiparallel.

20. The spintronic device as claimed in claim 16, wherein the second nonmagnetic layer has a thickness of a few nanometers.

21. The spintronic device as claimed in claim 20, wherein the material of the nonmagnetic layers is gold.

22. The spintronic device as claimed in claim 1, wherein the spin-polarized carriers are either electrons or holes.

23. An electronic memory of matrix structure, comprising at least one spintronic device as claimed in claim 1.