Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Resettable Instack Bias Using Direct Ferromagnetic / Antiferromagnetic Coupling

IP.com Disclosure Number: IPCOM000015941D
Original Publication Date: 2003-Feb-02
Included in the Prior Art Database: 2003-Jun-21
Document File: 2 page(s) / 99K

Publishing Venue

IBM

Abstract

Disclosed is an in-stack longitudinal bias scheme for magnetic multilayer sensors, utilizing a direct ferromagnetic or antiferromagnetic coupling to a biasing layer in close proximity to the sensing (free) layer of the sensor, and the shape anisotropy of the biasing layer itself. The ferromagnetic or antiferromagnetic coupling is achieved by properly adjusting/choosing the thickness and material of the non-magnetic spacer. By using direct coupling between the biasing layer and the free layer, our invention significantly simplify the complexity of the in-stack biasing structure. The result in an in-stach stabilized sensor structure of great simplicity, well suited for example to magnetic recording read heads with narrow shield-to-shield spacings as used for magnetic recording at densities > 100 Gbit/in2.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Resettable Instack Bias Using Direct Ferromagnetic / Antiferromagnetic Coupling

    Among numerous methods which can be used to stabilize the sense (free) layer in a magnetic sensor such as a spin-valve or tunnel-valve, some in-stack longitudinal bias schemes utilize a self-stabilized ferromagnetic layer (LBL2 as shown in Fig.1a, 1b). The LBL2 layer is stabilized by the shape anisotropy originating from the high aspect ratio between its width and its height. To subsequently stabilize the free layer of the sensor, one possible method involves a second LBL layer (LBL1 in Fig.1a), which is coupled to LBL2 through a strong antiparallel (AP) coupling accross a conducting spacer such as a thin Ru layer. LBL1 is patterned to the same dimensions as the free layer, so that magnetic flux emanating from the edges of LBL1 provides a longitudinal bias field which stabilizes the free layer. This approach however, requires the presence of two magnetic layers (LBL1 and LBL2) and therefore increases the total thickness of the sensor which is disadvantageous for obtaining the highest density recording sensors with the smallest shield-to-shield spacing. This approach is also fairly complicated to perfect as the properties of this additional magnetic layer must be optimized.

    In the present invention, the sense layer is stabilized by a direct ferromagnetic or antiferromagnetic coupling, without the need for an additional LBL1 layer. The ferromagnetic or antiferromagnetic coupling is achieved by properly adjusting/choosing the thickness and material of the non-magnetic spacer. It is widely known that the appropriate amount of antiferromagnetic (antiparallel) or ferromagnetic (parallel) coupling between the free layer and the LBL2 layer can be achieved by using RKKY indirect exchange coupling accross metallic spacers or Neel orange-peel magnetostatic coupling accross any spacer. For example, thin Ru, Cu or Cr layers are widely used for strong parallel or anti-parallel (depending on thickness) exchange coupling while simple rough magnetic layers display strong parallel magnetostatic coupling when placed on either side of a thin spacer layer (<50 Angstrom in thickness).

    By using direct coupling, our invention significantly simplif...