Magnetic devices and structures

• US 8,717,808 B2
• Filed: 06/06/2012
• Issued: 05/06/2014
• Est. Priority Date: 09/03/2009
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Hu, Guohan, Sun, Jonathan Z.
• Primary Examiner(s): Luu, Pho M
• Assistant Examiner(s): BUI, THA-O H
• Application Number:
  US13/489,746
• Publication Number:
  US 20120241885A1
• Time in Patent Office: 699 Days
• Field of Search: 365/148, 365/158, 365/171, 365/173
• US Class Current: 365/158
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell

Abstract

Magnetic devices, magnetoresistive structures, and methods and techniques associated with the magnetic devices and magnetoresistive structures are presented. For example, a magnetic device is presented. The magnetic device includes a ferromagnet, an antiferromagnet coupled to the ferromagnet, and a nonmagnetic metal proximate to the ferromagnet. The antiferromagnet provides uniaxial anisotropy to the magnetic device. A resistance of the nonmagnetic metal is dependent upon a direction of a magnetic moment of the ferromagnet.

Claims

1. A magnetic device comprising:

a ferromagnet layer;

an antiferromagnet layer coupled to the ferromagnet layer; and

a nonmagnetic metal proximate to the ferromagnet layer;

wherein the antiferromagnet layer provides uniaxial anisotropy to the ferromagnet layer, wherein an exchange coupling energy between the antiferromagnet layer and the ferromagnet layer is greater than energy associated with the uniaxial anisotropy to ensure concurrent rotation of magnetic moments of both the ferromagnet layer and the antiferromagnet layer under spin-torque excitation; and

wherein a resistance of the nonmagnetic metal is dependent upon a direction of the magnetic moment of the ferromagnet layer.

2. The magnetic device of claim 1, wherein a volume anisotropy of the antiferromagnet layer provides a thermal activation harrier for the magnetic device.

3. The magnetic device of claim 1, wherein the ferromagnet layer is a nanoferromagnet.

4. A magnetoresistive memory device comprising:

a ferromagnetic layer;

an antiferromagnetic layer coupled to the ferromagnetic layer, wherein a free side of the magnetoresistive memory device comprises the ferromagnetic layer and the antiferromagnetic layer;

a pinned layer having a magnetic moment in a fixed direction; and

a nonmagnetic metallic layer between the free side and the pimped layer;

wherein the antiferromagnetic layer provides uniaxial anisotropy to the ferromagnetic layer of the free side, wherein an exchange coupling energy between the antiferromagnetic layer and the ferromagnetic layer is greater than energy associated with the uniaxial anisotropy to ensure concurrent rotation of magnetic moments of both the ferromagnetic layer and antiferromagnetic layer under spin-torque excitation;

wherein a resistance of the nonmagnetic metallic layer is dependent upon a direction of the magnetic moment of the ferromagnetic layer in relation to the fixed direction of the magnetic moment of the pinned layer; and

wherein the magnetoresistive memory device stores at least two data states corresponding to at least two directions of the magnetic moment of the ferromagnetic layer.

5. The magnetoresistive memory device of claim 4, wherein the pinned layer comprises a pinned ferromagnetic layer and a pinned-side antiferromagnetic layer exchange-coupled to the pinned ferromagnetic layer.

6. An integrated circuit comprising:

a ferromagnetic layer;

an antiferromagnetic layer coupled to the ferromagnetic layer, wherein the ferromagnetic layer and the antiferromagnetic layer comprise a free side of a magnetoresistive structure;

a pinned layer having a magnetic moment in a fixed direction;

a nonmagnetic metallic layer between the free side and the pinned layer; and

a substrate on which the pinned layer, the nonmagnetic metallic layer, the ferromagnetic layer and the antiferromagnetic layer are formed;

wherein the antiferromagnetic layer provides uniaxial anisotropy to the ferromagnetic layer of the free side, wherein an exchange coupling energy between the antiferromagnetic layer and the ferromagnetic layer is greater than energy associated with the uniaxial anisotropy to ensure concurrent rotation of magnetic moments of both the ferromagnetic layer and the antiferromagnetic layer under spin-toque excitation; and

wherein a resistance of the nonmagnetic metallic layer is dependent upon a direction of the magnetic moment of the ferromagnetic layer in relation to the fixed direction of the magnetic moment of the pinned layer.

7. The integrated circuit of claim 6, wherein the pinned layer comprises a pinned ferromagnetic layer and a pinned-side antiferromagnetic layer exchange-coupled to the pinned ferromagnetic layer.

8. A method for forming a magnetoresistive structure, the method comprising the steps of:

forming a ferromagnetic layer;

forming an antiferromagnetic layer coupled to the ferromagnetic layer, wherein a free side of the magnetoresistive structure comprises the ferromagnetic layer and the antiferromagnetic layer;

forming a pinned layer having a magnetic moment in a fixed direction; and

forming a nonmagnetic metallic layer between the free side and the pinned layer;

wherein the antiferromagnetic layer provides uniaxial anisotropy to the ferromagnetic layer of the free side, wherein an exchange coupling energy between the antiferromagnetic layer and the ferromagnetic layer is greater than energy associated with the uniaxial anisotropy to ensure concurrent rotation of magnetic moments of both the ferromagnetic layer and the antiferromagnetic layer under spin-torque excitation; and

wherein a resistance of the nonmagnetic metallic layer is dependent upon a direction of a magnetic moment of the ferromagnetic layer in relation to the fixed direction of the magnetic moment of the pinned layer.

9. The method of claim 8, wherein forming the pinned layer comprises forming a pinned ferromagnetic layer and forming a pinned-side antiferromagnetic layer exchange-coupled to the pinned ferromagnetic layer.