EXCHANGE COUPLED MAGNETIC ELEMENTS

• US 20120251845A1
• Filed: 03/31/2011
• Published: 10/04/2012
• Est. Priority Date: 03/31/2011
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Wang, Xiaobin, Gao, Kaizhong
• Granted Patent: US 8,481,181 B2
• Time in Patent Office: Days
• US Class Current: 428/827
• CPC Class Codes: G11B 5/676 having magnetic layers separated by a nonmagnetic layer, e.g. antiferromagnetic layer, Cu layer or coupling layer
• CPC Class Codes: G11B 5/678 having three or more magnetic layers
• CPC Class Codes: Y10T 428/115 Magnetic layer composition

Abstract

Approaches to reduce switching field distribution in energy assisted magnetic storage devices involve first and second exchange coupled magnetic elements. The first magnetic elements have anisotropy, H_k1, volume, V₁ and the second magnetic elements are magnetically exchange coupled to the first magnetic elements and have anisotropy H_k2, and volume V₂. The thermal stability of the exchange coupled magnetic elements is greater than about 60 k_BT at a storage temperature of about 300 K. The magnetic switching field distribution, SFD, of the exchange coupled magnetic elements is less than about 200% at a predetermined magnetic switching field and a predetermined assisting switching energy.

Claims

1. A magnetic storage article, comprising:

first magnetic elements having anisotropy, H_k1, volume, V₁; and

second magnetic elements magnetically exchange coupled to the first magnetic elements, the second magnetic elements having anisotropy H_k2, and volume V₂, wherein a thermal stability of the exchange coupled magnetic elements is greater than about 60 k_BT at a storage temperature of about 300 K and a magnetic switching field distribution, SFD, of the exchange coupled magnetic elements is less than about 200% at a predetermined magnetic switching field and a predetermined assisting switching energy.

2. The article of claim 1, wherein the assisting switching energy comprises thermal energy.

3. The article of claim 1, wherein the assisting switching energy comprises microwave magnetic energy.

4. The article of claim 1, wherein the magnetic storage article comprises heat assisted magnetic recording (HAMR) medium.

5. The article of claim 1, wherein the magnetic storage article is a microwave assisted magnetic recording (MAMR) medium.

6. The article of claim 1, wherein the magnetic storage article is magnetoresistive random access memory (MRAM).

7. The article of claim 1, wherein the magnetic storage article comprises a patterned medium.

8. The magnetic article of claim 1, wherein each of the first and second magnetic elements have a volume less than about 10,000 nm³.

9. The article of claim 1, wherein the first magnetic elements have a saturation magnetization of M_s1, the second magnetic elements have a saturation magnetization of M_s2, and the ratio M_s2H_k2/M_s1H_k1 is less than about 0.8.

10. The article of claim 9, wherein M_s2 is equal to M_s1.

11. The article of claim 1, wherein the exchange field, h_ex=JM_s2/H_k1 is less than about 0.65, where J is the exchange coupling strength between the first grains and the second grains and M_s2 is the magnetization saturation of the second grains.

12. The article of claim 1, wherein the first and second grains are disposed in a single layer.

13. A magnetic storage article, comprising:

a first magnetic recording layer including first magnetic elements with anisotropy, H_k1, volume, V₁; and

a second magnetic recording layer including second magnetic elements magnetically exchange coupled to the first magnetic elements, the second magnetic elements having anisotropy H_k2, and volume V₂, wherein a thermal stability of the exchange coupled magnetic elements is greater than about 60 k_BT at a storage temperature of about 300 K and a magnetic switching field distribution, SFD, of the exchange coupled magnetic elements is less than about 200% at a switching temperature of greater than about 350 K.

14. The article of claim 13, wherein the first and second layers are continuous media layers.

15. The article of claim 14, wherein:

the second grains comprise CoPtX or CoCrPtX or CoCrX, where X is a non-magnetic metallic or non-metallic material; and

the first grains comprise FePtX or CoPtX with L1₀ structure.

16. The article of claim 14, wherein an exchange coupling layer is disposed between the first layer and the second layer.

17. The article of claim 14, wherein the exchange coupling layer comprises MgO, Mg, or Ag.

18. The article of claim 13, wherein the second magnetic elements have a Curie temperature, T_c2, and T_c2 is not equal to a Curie temperature of the first magnetic elements, T_c1.

19. The article of claim 13, wherein each of the first and second magnetic elements have a volume less than about 10,000 nm³.

20. The article of claim 13, wherein H_k1 is about equal to K_k2, an aspect ratio of the first and second magnetic elements is substantially the same, and V₁ is not equal to V₂.