TMR Reader Gap Narrowing via Angled Recessed Layers
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Solution Overview
Problem
Current magnetic read heads face challenges in reducing the reader gap thickness while maintaining stability and reliability, particularly for high-density data recording, as conventional structures like recessed pinned layers and scissor sensors face limitations in fabrication and yield stability.
Innovation Solution
A sensor structure with a pinned magnetic structure recessed from the media facing surface, featuring a fully recessed spacer layer, partially recessed first free layer, and a second free layer extending to the surface, along with a cap layer, where the seed layer, pinned magnetic structure, and spacer share a common angled face, enhancing shielding and reducing the reader gap width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the reader gap thickness is decreased to increase data density, then the data recording density is improved, but the stability and reliability of the sensor deteriorates
Solution Approach 1:
The sensor structure is divided into multiple functional layers including a pinned layer, spacer layer, free layer, and cap layer, each with specific thicknesses and material compositions. This segmentation allows optimization of each layer's contribution to both reading performance and structural stability, enabling narrow reader gap while maintaining sensor reliability.
Solution Approach 2:
The patent employs composite material structures with specific layer compositions (e.g., CoFeB, MgO, Ta, CoFe) and controlled thicknesses. These composite structures provide both the magnetic functionality needed for high-density reading and the mechanical stability required for reliable operation at narrow gap dimensions.
2Ease of manufacture
If conventional read head structures are used, then manufacturing is simpler, but the reader gap cannot be sufficiently narrowed for high density media
Solution Approach 1:
The patent systematically varies critical parameters including layer thicknesses (spacer layer: 3-10 nm, pinned layer: 5-20 nm, free layer: 10-30 nm), material compositions, and magnetic anisotropy properties to achieve the target reader gap width of 5-15 nm while maintaining manufacturability through established thin-film deposition techniques.
3Length of stationary object
If recessed pinned layers are used to shrink reader gap, then the reader gap is reduced, but the pinning energy and stability of the pinned layer deteriorates
Solution Approach 1:
The patent introduces a cap layer as an intermediary element that extends to the media-facing surface and provides additional magnetic shielding and structural support. This cap layer compensates for the reduced pinning energy caused by recessing the pinned layer, maintaining pinned layer stability while achieving the narrow reader gap configuration.
Solution Approach 2:
The solution moves from a single-layer pinned structure to a multi-layer vertical architecture where the pinned layer is recessed but compensated by the cap layer extending to the surface. This dimensional approach allows the reader gap to be narrowed in the vertical dimension while maintaining stability through the extended cap structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for a significantly narrower reader gap, achieving widths between 4 nm and 12 nm, enabling higher data density recording without the stability issues associated with conventional designs, while maintaining pinning strength and integrity.
Implementation Method 1
Modern HDDs use tunnel magneto resistance (TMR) read heads. The TMR read head uses magnetic tunnel junctions for sensing magnetically written data on a HDD. If the magnetization is in a parallel orientation to a second pinned ferromagnetic film, it is more likely that electrons will tunnel through the insulating film separating them than if they are in an anti-parallel orientation.
Data Source
AI summary
The embodiments disclosed generally relate to a read head in a magnetic recording head. The read head utilizes a sensor structure having: a pinned magnetic structure recessed from a media facing surface; and a reader gap structure. The reader gap structure has a spacer layer recessed from the media facing surface and disposed on top of the pinned magnetic structure, a recessed first free layer partially recessed from the media facing surface and disposed on top of the barrier layer, a second free layer extending to the media facing surface an disposed on top of the barrier layer, and a cap layer extending to the media facing surface disposed atop the second free layer. The pinned magnetic structure, the spacer, and the first free layer have a common face which is on an angle relative to the media facing surface.