Magnetic Read Head Stability via Fixed Layer Extension
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Solution Overview
Problem
The miniaturization of magnetic read heads for higher recording density in hard disk drives leads to instability issues due to the reduced size of the fixed layer, resulting in an insufficient biasing magnetic field for the free layer, especially when using soft magnetic domain control films.
Innovation Solution
A magnetic read head design where the fixed layer extends beyond the free layer in the cross-track direction, with magnetic domain control films on both sides comprising a soft magnetic material, and the free layer and domain control films are etched to the same height to ensure a strong biasing magnetic field, enhancing stability and read resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the fixed layer is miniaturized to achieve higher recording density, then the recording capacity increases, but the stability of the fixed layer deteriorates and the biasing magnetic field becomes insufficient
Solution Approach 1:
The patent extends the fixed layer in the cross-track direction (lateral dimension) beyond the free layer boundaries, creating a broader base that provides enhanced stability and stronger biasing magnetic field without increasing the vertical height or compromising the miniaturized footprint required for high recording density.
Solution Approach 2:
The fixed layer is designed with non-uniform dimensions: it is narrow in the track direction (to maintain high recording density) but extends wider in the cross-track direction (to provide stability and biasing field). This local variation in geometry allows simultaneous optimization of both recording capacity and fixed layer stability.
2Force
If soft magnetic domain control films are used instead of hard magnetic films, then the biasing magnetic field strength improves, but the stability of the fixed layer deteriorates due to insufficient field confinement
Solution Approach 1:
By extending the fixed layer laterally in the cross-track direction beyond the free layer, the patent creates a broader magnetic field distribution region. This lateral extension allows soft magnetic domain control films to generate stronger biasing fields while the extended fixed layer provides sufficient field confinement and stability through its broader base.
Solution Approach 2:
The extended fixed layer acts as an intermediary structure that mediates between the soft magnetic domain control films and the free layer. It provides a stable foundation that confines the magnetic field while allowing the soft magnetic films to exert their full biasing effect on the free layer without compromising fixed layer stability.
3Ease of manufacture
If the free layer and domain control films are etched to different heights, then the manufacturing process is simpler, but the biasing magnetic field strength is reduced
Solution Approach 1:
The patent performs a preliminary etching step that removes domain control film material adjacent to the free layer before final assembly. This preliminary action creates the necessary geometric configuration where the free layer and domain control films are etched to the same height, ensuring strong biasing magnetic field while maintaining manufacturing feasibility through staged processing.
Solution Approach 2:
The patent replaces complex multi-height etching mechanisms with a simplified single-height etching process. By designing the structure so that both free layer and domain control films are etched to the same height, the manufacturing process is simplified while the extended fixed layer geometry compensates by providing sufficient field confinement and biasing strength.
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 design improves the stability and read resolution of the magnetic read head by maintaining a strong biasing magnetic field while maintaining the fixed layer's stability, even with soft magnetic domain control films, ensuring effective data storage performance.
Implementation Method 1
a fixed layer having a first ferromagnetic material that has a direction of magnetization that is fixed
Implementation Method 2
a fixed layer having a first ferromagnetic material that has a direction of magnetization that is fixed
Implementation Method 3
magnetic domain control films positioned on both sides of the free layer at a media-facing surface in the cross-track direction, the magnetic domain control films including a soft magnetic material
Implementation Method 4
The read output is therefore obtained by sensing a change of the film resistance produced by rotation of the magnetization of the free layer in response to the direction of the leakage magnetic field from each of the recording bits on the recording medium
Implementation Method 5
a direction of magnetization of the upper ferromagnetic layer (e.g., a free layer) is rotated by a leakage magnetic field produced from the recording medium
Implementation Method 6
a direction of magnetization of the upper ferromagnetic layer (e.g., a free layer) is rotated by a leakage magnetic field produced from the recording medium
Data Source
AI summary
In one embodiment, a method for forming a magnetoresistive read head includes forming a fixed layer having a first ferromagnetic material that has a fixed direction of magnetization above a lower shield layer, forming a free layer having a second ferromagnetic material positioned above the fixed layer, the free layer having a non-fixed direction of magnetization, forming a first mask above the free layer, the first mask having a predetermined width based on a track width of a magnetic medium, etching the free layer down to the fixed layer using the first mask as a guide, wherein substantially none of the fixed layer is etched, and wherein the fixed layer extends beyond both sides of the free layer in a cross-track direction, and forming magnetic domain control films on both sides of the free layer in the cross-track direction, the magnetic domain control films including a soft magnetic material.