Method and system for providing a read transducer having symmetric antiferromagnetically coupled shields

• US 10,074,387 B1
• Filed: 12/21/2014
• Issued: 09/11/2018
• Est. Priority Date: 12/21/2014
• Status: Active Grant

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital (Fremont) LLC (Western Digital Corporation)
• Inventors: Xiao, Rongfu, Wang, Miaoyin, Zhang, Zhihong, Luo, Guanghong, Mao, Ming
• Primary Examiner(s): Cazan, Livius R
• Application Number:
  US14/578,450
• Time in Patent Office: 1,360 Days
• CPC Class Codes: G11B 2005/3996 large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11B 5/3912 Arrangements in which the active read-out elements are transducing in association with active magnetic shields, e.g. magnetically coupled shields G11B5/3916 takes precedence

Abstract

A method provides a magnetic transducer including a first antiferromagnetically coupled (AFC) shield, a second AFC shield and a read sensor between the first and second AFC shields. The first AFC shield includes first and second ferromagnetic layers and a first nonmagnetic spacer layer between the first and second ferromagnetic layers. The first and second ferromagnetic layers have first and second saturation magnetizations and first and second thicknesses, respectively. The second ferromagnetic layer is between the read sensor and the first ferromagnetic layer. The second AFC shield includes third and fourth ferromagnetic layers and a second nonmagnetic spacer layer between the third and fourth ferromagnetic layers. The third ferromagnetic layer is between the read sensor and the fourth ferromagnetic layer. The third and fourth ferromagnetic layers have third and saturation magnetizations and third and fourth thicknesses, respectively. The second AFC shield is a mirror image of the first AFC shield.

Claims

1. A magnetic read transducer having an air-bearing surface (ABS), comprising:

a first antiferromagnetically-coupled (AFC) shield, the first AFC shield including a first ferromagnetic layer, a second ferromagnetic layer and a first nonmagnetic spacer layer between the first ferromagnetic layer and the second ferromagnetic layer, the first ferromagnetic layer having a first saturation magnetization and a first thickness, the second ferromagnetic layer having a second saturation magnetization and a second thickness, wherein there is a first difference between the first ferromagnetic layer and the second ferromagnetic layer, the first difference including at least one of a difference between the first thickness and the second thickness or a difference between compositions of the first ferromagnetic layer and the second ferromagnetic layer;

a read sensor, the second ferromagnetic layer being between the read sensor and the first ferromagnetic layer; and

a second AFC shield, the second AFC shield including a third ferromagnetic layer, a fourth ferromagnetic layer and a second nonmagnetic spacer layer between the third ferromagnetic layer and the fourth ferromagnetic layer, the third ferromagnetic layer being between the read sensor and the fourth ferromagnetic layer, the third ferromagnetic layer having a third saturation magnetization and a third thickness, the fourth ferromagnetic layer having a fourth saturation magnetization and a fourth thickness, wherein there is a second difference between the third ferromagnetic layer and the fourth ferromagnetic layer that corresponds to the first difference such that the second AFC shield is a mirror image of the first AFC shield,

wherein the second saturation magnetization multiplied by the second thickness matches the third saturation magnetization multiplied by the third thickness to within twenty percent and the first saturation magnetization multiplied by the first thickness matches the fourth saturation magnetization multiplied by the fourth thickness to within twenty percent,

wherein the second thickness is different from the third thickness and the second ferromagnetic layer is made of different materials than materials in the third ferromagnetic layer, or the first thickness is different from the fourth thickness and the first ferromagnetic layer is made of different materials than materials in the fourth ferromagnetic layer.

2. The magnetic read transducer of claim 1 wherein the second ferromagnetic layer has a second ferromagnetic layer magnetic moment that is antiferromagnetically-aligned with a third ferromagnetic layer magnetic moment of the third ferromagnetic layer.

3. The magnetic read transducer of claim 1 wherein the second ferromagnetic layer has a second ferromagnetic layer magnetic moment that is aligned parallel with a third ferromagnetic layer magnetic moment of the third ferromagnetic layer.

4. The magnetic read transducer of claim 1 wherein the second AFC shield further includes

a pinning layer magnetically-coupled with the fourth ferromagnetic layer.

5. The magnetic read transducer of claim 4 wherein the first AFC shield further includes

an additional pinning layer magnetically-coupled with the first ferromagnetic layer.

6. The magnetic read transducer of claim 1 wherein the first AFC shield further includes

a first CoFeB layer and the second AFC shield further includes

a second CoFeB layer.

7. The magnetic read transducer of claim 1 further comprising

a bottom shield, the first AFC shield residing on the bottom shield.

8. The magnetic read transducer of claim 7 further comprising

a nonmagnetic layer on the bottom shield, the nonmagnetic layer being between the first AFC shield and the bottom shield.

9. The magnetic read transducer of claim 8 wherein the nonmagnetic layer is planarized.

10. The magnetic read transducer of claim 7 further comprising

a top shield residing on the second AFC shield.

11. The magnetic read transducer of claim 10 further comprising

an additional nonmagnetic layer on the second AFC shield, the additional nonmagnetic layer being between the second AFC shield and the top shield.

15. A data storage device comprising the magnetic read transducer of claim 1.

12. A method for providing a magnetic read transducer having an air-bearing surface (ABS), comprising:

providing a bottom shield;

providing a first nonmagnetic layer on the bottom shield;

planarizing the first nonmagnetic layer;

providing a first antiferromagnetically-coupled (AFC) shield on the first nonmagnetic layer, the first AFC shield including a first ferromagnetic layer, a second ferromagnetic layer and a first nonmagnetic spacer layer between the first ferromagnetic layer and the second ferromagnetic layer, the first ferromagnetic layer having a first magnetic moment and a first thickness, the second ferromagnetic layer having a second magnetic moment and a second thickness, wherein there is a first difference between the first ferromagnetic layer and the second ferromagnetic layer, the first difference including at least one of a difference between the first thickness and the second thickness or a difference between compositions of the first ferromagnetic layer and the second ferromagnetic layer;

providing a read sensor, the second ferromagnetic layer being between the read sensor and the first ferromagnetic layer; and

providing a second AFC shield, the second AFC shield including a third ferromagnetic layer, a fourth ferromagnetic layer and a second nonmagnetic spacer layer between the third ferromagnetic layer and the fourth ferromagnetic layer, the third ferromagnetic layer being between the read sensor and the fourth ferromagnetic layer, the third ferromagnetic layer having a third magnetic moment and a third thickness, the fourth ferromagnetic layer having a fourth magnetic moment and a fourth thickness, wherein there is a second difference between the third ferromagnetic layer and the fourth ferromagnetic layer that corresponds to the first difference such that the second AFC shield is a mirror image of the first AFC shield,

wherein the first ferromagnetic layer has a first saturation magnetization, the second ferromagnetic layer has a second saturation magnetization, the third ferromagnetic layer has a third saturation magnetization, and the fourth ferromagnetic layer has a fourth saturation magnetization,

wherein the second saturation magnetization multiplied by the second thickness matches the third saturation magnetization multiplied by the third thickness to within twenty percent and the first saturation magnetization multiplied by the first thickness matches the fourth saturation magnetization multiplied by the fourth thickness to within twenty percent,

wherein the second thickness is different from the third thickness and the second ferromagnetic layer is made of different materials than materials in the third ferromagnetic layer, or the first thickness is different from the fourth thickness and the first ferromagnetic layer is made of different materials than materials in the fourth ferromagnetic layer;

providing a second nonmagnetic layer on the second AFC shield; and

providing a top shield residing on the second nonmagnetic layer.

13. The method of claim 12 wherein the step of providing the first AFC shield further includes:

depositing at least a first layer for the first ferromagnetic layer on the first nonmagnetic layer;

depositing a second layer for the first nonmagnetic spacer layer on the at least the first layer;

depositing at least a third layer for the second ferromagnetic layer on the second layer;

providing a mask covering a portion of the at least the third layer corresponding to the second ferromagnetic layer; and

removing a portion of the at least the first layer, the second layer and the at least the third layer exposed by the mask, such that the first ferromagnetic layer, first nonmagnetic layer, and the second ferromagnetic layer of the first AFC shield remain.

14. The method of claim 12 wherein the step of providing the first AFC shield further includes:

providing a mask exposing a portion of the first nonmagnetic layer corresponding to the first AFC shield;

removing a portion of the first nonmagnetic layer exposed by the mask to form a shield trench;

depositing at least a first layer for the first ferromagnetic layer, a portion of the at least the first layer residing in the shield trench corresponding to the first ferromagnetic layer;

depositing a second layer for the first nonmagnetic spacer layer on the at least the first layer, a portion of the second layer residing in the shield trench corresponding to the first nonmagnetic spacer layer;

depositing at least a third layer for the second ferromagnetic layer on the second layer, a portion of the at least the third layer residing in the shield trench corresponding to the second ferromagnetic layer;

removing the mask such that the first ferromagnetic layer, the second ferromagnetic layer and the first nonmagnetic spacer layer remaining in the shield trench form the first AFC shield.