Magnetoresistive sensor with pinned SAL

• US 6,137,662 A
• Filed: 04/07/1998
• Issued: 10/24/2000
• Est. Priority Date: 04/07/1998
• Status: Expired due to Term

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Read-Rite Corporation (Western Digital Corporation)
• Inventors: Nepela, Daniel, Huai, Yiming, Lederman, Marcos, Ravipati, Durga
• Primary Examiner(s): Korzuch, William R.
• Application Number:
  US09/055,730
• Time in Patent Office: 931 Days
• Field of Search: 360/113, 360/314, 360/315, 360/324, 360/324.11, 360/327.22, 338/32 R, 324/207.21
• US Class Current: 360/327.22
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G01R 33/096 anisotropic magnetoresistance sensors
• 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 5/3903 using magnetic thin film layers or their effects, the films being part of integrated structures
• CPC Class Codes: G11B 5/3932 Magnetic biasing films

Abstract

A magnetoresistive sensor including a magnetoresistive (MR) sensing element, a nonmagnetic layer ("spacer") contacting the magnetoresistive sensing element; a first antiferromagnetic (AFM) layer contacting the nonmagnetic layer such that the nonmagnetic layer is sandwiched between the magnetoresistive sensing element and the antiferromagnetic layer; a ferromagnetic soft adjacent layer (SAL) contacting the antiferromagnetic layer such that the antiferromagnetic layer is sandwiched between the nonmagnetic layer and the soft adjacent layer; and a second antiferromagnetic layer contacting the SAL such that the SAL is sandwiched between the first and second antiferromagnetic layers. The two antiferromagnetic layers provide a stronger pinning effect. In one embodiment of the invention, the magnetoresistive sensing element is an anisotropic magnetoresistive (AMR) sensing element comprising a soft ferromagnetic layer. In another embodiment of the invention, the magnetoresistive sensing element is giant magnetoresistive (GMR) sensing element comprising a plurality of layers. The bias scheme can be non-symmetric, or may be symmetric around the magnetoresistive sensing element. An exchange biased bilayer (AFM/SAL) can have a multilayered structure such as AFM/SAL/AFM/SAL. . . . In this configuration, the SAL layer can be thin, so that a high exchange field with a high resistance can be obtained.

Claims

1. A magnetoresistive sensor comprising:

a magnetoresistive sensing element;

a first nonmagnetic layer contacting said magnetoresistive sensing element;

a first antiferromagnetic layer contacting said first nonmagnetic layer such that said first nonmagnetic layer is sandwiched between said magnetoresistive sensing element and said first antiferromagnetic layer;

a first ferromagnetic soft adjacent layer contacting said first antiferromagnetic layer such that said first antiferromagnetic layer is sandwiched between said nonmagnetic layer and said first soft adjacent layer;

a second nonmagnetic layer contacting said magnetoresistive sensing element such that said magnetoresistive sensing element is sandwiched between said first nonmagnetic layer and said second nonmagnetic layer;

a second antiferromagnetic layer contacting said second nonmagnetic layer such that said second nonmagnetic layer is sandwiched between said second antiferromagnetic layer and said magnetoresistive sensing element;

a second ferromagnetic soft adjacent layer contacting said second antiferromagnetic layer such that said second antiferromagnetic layer is sandwiched between said second nonmagnetic layer and said second soft adjacent layer; and

a third antiferromagnetic layer contacting said first soft adjacent layer such that said first soft adjacent layer is sandwiched between said first antiferromagnetic layer and said third antiferromagnetic layer.

2. A magnetoresistive sensor comprising:

a magnetoresistive sensing element;

a first nonmagnetic layer contacting said magnetoresistive sensing element;

a first antiferromagnetic layer contacting said first nonmagnetic layer such that said first nonmagnetic layer is sandwiched between said magnetoresistive sensing element and said first antiferromagnetic layer;

a first ferromagnetic soft adjacent layer contacting said first antiferromagnetic layer such that said first antiferromagnetic layer is sandwiched between said first nonmagnetic layer and said first soft adjacent layer;

a second antiferromagnetic layer contacting said first soft adjacent layer such that said first soft adjacent layer is sandwiched between said first antiferromagnetic layer and said second antiferromagnetic layer;

a second nonmagnetic layer contacting said magnetoresistive sensing element such that said magnetoresistive sensing element is sandwiched between said first nonmagnetic layer and said second nonmagnetic layer;

a third antiferromagnetic layer contacting said second nonmagnetic layer such that said second nonmagnetic layer is sandwiched between said magnetoresistive sensing element and said third antiferromagnetic layer;

a second ferromagnetic soft adjacent layer contacting said third antiferromagnetic layer such that said third antiferromagnetic layer is sandwiched between said second nonmagnetic layer and said second soft adjacent layer; and

a fourth antiferromagnetic layer contacting said second soft adjacent layer such that said second soft adjacent layer is sandwiched between said third antiferromagnetic layer and said fourth antiferromagnetic layer.

3. A magnetoresistive sensor as recited in claim 2 wherein

said first nonmagnetic layer and said second nonmagnetic layer are made from essentially the same material;

said first antiferromagnetic layer, said second antiferromagnetic layer, said third antiferromagnetic layer, and said fourth antiferromagnetic layer are made from essentially the same material; and

said first soft adjacent layer and said second soft adjacent layer are made from essentially the same material.