High Moment Wrap Shields for Magnetic Read Head Micro-Magnetic Read Width
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Solution Overview
Problem
Current thin-film magnetoresistive read sensors face challenges in achieving high micro-magnetic read width sharpness due to demagnetization interference from external fields, particularly as sensor dimensions shrink, and conventional hard bias layers with randomly distributed grains become less effective.
Innovation Solution
The use of high magnetic moment wrap shields on the side and top shields, formed without a seed layer, with a thin layer of high magnetic moment Fe or Fe-containing materials directly on insulation layers to reduce gap width and prevent pinning, while aligning magnetization anisotropy through annealing, enhances sensor stability and read width sharpness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hard bias layers are used to provide longitudinal biasing, then the sensor can be biased to stabilize magnetization, but the randomly distributed hard magnetic grains cause instability and reduced read width sharpness
Solution Approach 1:
The patent changes the magnetic properties of the bias layer by using soft magnetic materials (low coercivity) instead of hard magnetic materials (high coercivity). This parameter change in magnetic properties allows for stable magnetization biasing while eliminating the grain distribution problems that degrade read width sharpness
Solution Approach 2:
The patent employs composite shield structures combining soft magnetic materials with high magnetic moment materials. This composite approach provides both the biasing stability from soft magnets and the magnetic field concentration from high moment materials, improving read width sharpness while maintaining magnetization stability
2Productivity
If sensor dimensions are reduced to match nanometer-scale recording bits, then recording density increases, but demagnetization interference from external fields becomes more significant
Solution Approach 1:
The patent applies local quality by creating shield structures with non-uniform magnetic properties around the sensor. The shields have different magnetic moments and coercivities in different regions, providing localized magnetic field control that compensates for demagnetization interference at the sensor edges while maintaining high recording density
Solution Approach 2:
The shield structure acts as an intermediary between the sensor and external magnetic fields. The shields with specific magnetic moment properties mediate the interaction, providing biasing fields that counteract demagnetization interference from external sources while allowing the sensor to read nanometer-scale bits
3Measurement precision
If the gap between the free layer and biasing layer is reduced to improve read width sharpness, then micro-magnetic read width sharpness improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes the magnetic moment parameter of the shield materials to achieve the desired gap width effect. By selecting materials with specific magnetic moments, the patent can achieve the necessary magnetic field coupling at reduced gaps without requiring extremely tight dimensional tolerances, thus improving read width sharpness while managing manufacturing precision requirements
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 improves micro-magnetic read width sharpness and stability by reducing the gap between the free layer and biasing layer, preventing unwanted pinning, and aligning magnetization, resulting in enhanced sensor performance and recording density.
Implementation Method 1
The side shields are formed of a magnetically soft material having a low coercivity and a high magnetic moment... the magnetization of the high moment layer and the soft magnetic layer in the side shields by annealing in a longitudinal magnetic field
Implementation Method 2
When an external magnetic field is applied to the sensor by passing it over a recording medium at its ABS, the FL magnetization will rotate corresponding to the direction of the magnetic field it experiences
Implementation Method 3
aligning the anisotropy or the magnetization of the high moment layer and the soft magnetic layer in the side shields by annealing under magnetic field along the longitudinal direction for efficient biasing of the free layer
Implementation Method 4
aligning the anisotropy or the magnetization of the high moment layer and the soft magnetic layer in the side shields by annealing
Implementation Method 5
Current technology utilizes the tunneling magnetoresistive (TMR) effect in the SVMR sensor... the resistance R will change in accord with the joint magnetization states of FL and An R is low when the magnetization of the FL is parallel to the AP1 and high when antiparallel
Implementation Method 6
The layer AP1 is pinned by yet another ferromagnetic layer (AP2, for 'second antiparallel layer') through a synthetic anti-ferromagnetic (SAF) effect which creates antiparallel magnetic moments in AP1 and AP2
Data Source
AI summary
A magnetically stable, read sensor uses low-coercivity magnetic material without seed layers in side shields for longitudinal biasing in order to improve micro-magnetic read width of the sensor. The sensor is formed between an upper and lower shield and includes a symmetric pair of abutting side shields adjacent to the sides of the sensor. In one configuration the side shields are partially covered by a layer of high magnetic moment material that extends along a bottom surface and side surface of the side shields and is contiguous and conformal with the layer of insulating material, but does not cover the backside of the sensor. The high moment layer focuses flux at the sensor sides and also improves the micro-magnetic read width. The side shields include a multiplicity of horizontal ferromagnetic layers that are antiferromagnetically coupled to each other and magnetically coupled to the upper shield.