Magnetic element with dual magnetic states and fabrication method thereof

• US 6,233,172 B1
• Filed: 12/17/1999
• Issued: 05/15/2001
• Est. Priority Date: 12/17/1999
• Status: Expired due to Term

• Current Assignee: Everspin Technologies Incorporated
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Chen, Eugene Youjun, DeHerrera, Mark, Durlam, Mark, Tehrani, Saied N., Slaughter, Jon Michael
• Primary Examiner(s): Dinh, Son T.
• Application Number:
  US09/464,807
• Time in Patent Office: 515 Days
• Field of Search: 365/171, 365/158, 365/173
• US Class Current: 365/173
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01F 10/3272 by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets

Abstract

An improved and novel magnetic element (10; 10′; 50; 50′; 80) including a plurality of thin film layers wherein the bit end magneto-static demagnetizing fields cancel the total positive coupling of the structure to obtain dual magnetic states in a zero external field. Additionally disclosed is a method of fabricating a magnetic element (10) by providing a plurality of thin film layers wherein the bit end magneto-static demagnetizing fields of the thin film layers cancel the total positive coupling of the structure to obtain dual magnetic states in a zero external field.

Claims

1. A magnetic element comprising a plurality of thin film layers wherein a plurality of bit end magneto-static demagnetization fields cancel the total positive coupling of the magnetic element to obtain dual magnetic states in a zero external field.

2. A magnetic element as claimed in claim 1 wherein the plurality of thin film layers form one of a spin valve structure or a magnetic tunnel junction (MTJ) structure.

3. A magnetic element as claimed in claim 2 wherein the plurality of thin film layers form a SAF structure having a fixed ferromagnetic layer and a pinned ferromagnetic layer, the fixed ferromagnetic layer having a thickness greater than the pinned ferromagnetic layer thereby canceling positive coupling between the fixed ferromagnetic layer and a free ferromagnetic layer.

4. A magnetic element as claimed in claim 2 wherein the plurality of thin film layers form a structure including a plurality of ferromagnetic layers having differing switching fields, wherein an offset between the ferromagnetic layers provides for a decrease in the demagnetizing field between the ferromagnetic layers thereby canceling positive coupling between the ferromagnetic layers.

5. A magnetic element as claimed in claim 4 wherein the plurality of ferromagnetic layers include a pinned ferromagnetic layer and a free ferromagnetic layer, and the offset provides for a decrease in the demagnetizing field from the pinned ferromagnetic layer to the free ferromagnetic layer thereby canceling positive coupling between the pinned ferromagnetic layer and the free ferromagnetic layer.

6. A magnetic element as claimed in claim 2 wherein the plurality of thin film layers form a structure including a free ferromagnetic layer, a plurality of spacer layers, and a plurality of ferromagnetic layers having antiparallel alignment due to end-magneto static coupling, wherein the thickness of at least one of the plurality of ferromagnetic layers is adjusted to provide for the canceling of positive coupling between the free ferromagnetic layer and at least one of the plurality of ferromagnetic layers.

7. A magnetic element comprising:

a first electrode comprising a fixed ferromagnetic layer whose magnetization is fixed in a preferred direction in the presence of an applied magnetic field having a specific strength, the fixed ferromagnetic layer having a thickness₁ (t₁), a pinned ferromagnetic layer having a thickness₂ (t₂) and a coupling interlayer located between the fixed ferromagnetic layer and the pinned ferromagnetic layer;

a second electrode comprising a free ferromagnetic layer having a surface whose magnetization is free to rotate in the presence of a sufficient applied magnetic field;

a spacer layer located between the fixed ferromagnetic layer of the first electrode and the free ferromagnetic layer of the second electrode;

wherein the thickness t₁, of the fixed ferromagnetic layer is greater than the thickness t₂ of the pinned ferromagnetic layer thereby canceling positive coupling between the fixed ferromagnetic layer and the free ferromagnetic layer; and

a substrate, the first and second electrodes, and the spacer layer, being formed on the substrate.

8. A magnetic element as claimed in claim 7 wherein the pinned ferromagnetic layer has its magnetization fixed by an antiferromagnetic pinning layer, and the fixed ferromagnetic layer is fixed in the opposite direction by antiferromagnetic exchange to the pinned ferromagnetic layer through a coupling interlayer, thereby defining a SAF structure.

9. A magnetic element as claimed in claim 7 wherein the coupling interlayer is formed of ruthenium (Ru).

10. A magnetic element as claimed in claim 7 further including at least one offset between the free ferromagnetic layer and the spacer layer.

11. A magnetic element as claimed in claim 7 wherein the spacer layer includes one of a dielectric material defining a MTJ structure or a conductive material defining a spin valve structure.

12. A magnetic element comprising:

a first electrode comprising a pinned ferromagnetic layer whose magnetic moment is pinned in a preferred direction in the presence of an applied magnetic field characterized as having a specific strength;

a second electrode comprising a free ferromagnetic layer having a surface whose magnetization is free to rotate in the presence of a sufficient applied magnetic field;

a spacer layer located between the pinned ferromagnetic layer of the first electrode and the free ferromagnetic layer of the second electrode;

wherein an offset provides for a decrease in the demagnetizing field from the pinned ferromagnetic layer to the free ferromagnetic layer thereby canceling positive coupling between the pinned ferromagnetic layer and the free ferromagnetic layer; and

a substrate, the first and second electrodes, and the spacer layer, being formed on the substrate.

13. A magnetic element as claimed in claim 12 wherein the spacer layer includes one of a dielectric material defining a MTJ structure or a conductive material defining a spin valve structure.

14. A method of fabricating a magnetic element comprising the step of providing a plurality of thin film layers wherein a plurality of bit end magneto-static demagnetizing fields cancel the total positive coupling of the magnetic element to obtain dual magnetic states in a zero external field.

15. A method of fabricating a magnetic element as claimed in claim 14 wherein the step of providing a plurality of thin film layers includes the step of providing the plurality of thin film layers to form one of a spin valve structure or a magnetic tunnel junction (MTJ) structure.

16. A method of fabricating a magnetic element as claimed in claim 15 wherein the step of providing a plurality of thin film layers includes the step of forming a SAF structure having a fixed ferromagnetic layer and a pinned ferromagnetic layer, the fixed ferromagnetic layer having a thickness greater than the pinned ferromagnetic layer thereby canceling positive coupling between the fixed ferromagnetic layer and a free ferromagnetic layer.

17. A method of fabricating a magnetic element as claimed in claim 15 wherein the step of providing a plurality of thin film layers includes the step of forming a structure including a plurality of ferromagnetic layers having differing switching fields, wherein an offset between the ferromagnetic layers provides for a decrease in the demagnetizing field between the ferromagnetic layers thereby canceling positive coupling between the ferromagnetic layers.

18. A magnetic element as claimed in claim 17 wherein the step of providing a plurality of ferromagnetic layers includes the step of forming a pinned ferromagnetic layer and a free ferromagnetic layer, and the offset provides for a decrease in the demagnetizing field from the pinned ferromagnetic layer to the free ferromagnetic layer thereby canceling positive coupling between the pinned ferromagnetic layer and the free ferromagnetic layer.

19. A method of fabricating a magnetic element as claimed in claim 15 wherein the step of providing a plurality of thin film layers includes the step of forming a structure including a free ferromagnetic layer, a plurality of spacer layers, and a plurality of ferromagnetic layers having antiparallel alignment due to end-magneto static coupling, wherein the thickness of at least one of the plurality of ferromagnetic layers is adjusted to provide for the canceling of positive coupling between the free ferromagnetic layer and at least one of the plurality of ferromagnetic layers.