Multi-Sensor Magnetic Head With Back Side Antiferromagnetic Shield
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Solution Overview
Problem
Magnetic heads with multi-sensor readers face challenges in reading data from inner and outer tracks of magnetic disks due to skew angles, leading to errors caused by misalignment of sensors, which increases noise and decreases sensitivity.
Innovation Solution
A magnetic head design incorporating a lower magnetic shield, a lower sensor with a free layer, a middle magnetic shield, and a backside antiferromagnetic (AFM) layer provides magnetic stabilization, reducing the distance between sensors and allowing for accurate data reading across varying track pitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-sensor readers with staggered or offset sensors are used to increase recording density, then sensitivity is improved, but sensor misalignment occurs on inner and outer tracks leading to reading errors
Solution Approach 1:
The patent introduces a skew angle between the sensor array and the track direction, allowing the sensor positions to dynamically adapt to different track radii. This dynamic geometric relationship ensures that sensors remain properly aligned with their respective tracks across the disk surface, resolving the misalignment issue while preserving the sensitivity benefits of multi-sensor configuration
Solution Approach 2:
The patent changes the geometric parameters of the sensor arrangement by introducing a skew angle and optimizing sensor spacing. This parameter modification allows the sensor array to maintain proper alignment with tracks of varying radii, eliminating reading errors while preserving the enhanced sensitivity achieved through multi-sensor configuration
2Quantity of substance
If sensor track width is narrowed to increase recording density, then areal density is improved, but element resistance and electrical noise increase
Solution Approach 1:
The patent divides the sensing function across multiple sensors arranged in an array, with each sensor reading from a wider track. By segmenting the read function across multiple elements, the system achieves high areal density without requiring individual sensors to be narrowly confined, thereby avoiding the noise and resistance penalties associated with miniaturized single sensors
Solution Approach 2:
The patent combines signals from multiple sensors to achieve the equivalent of a narrow track read while using physically wider sensors. By merging the output signals from multiple wider sensors through signal processing, the system achieves the density benefits of narrow tracking without the harmful electrical effects of miniaturized sensor elements
3Measurement precision
If distance between lower sensor and upper sensors is increased in MIMO configuration, then sensitivity is improved, but head profile becomes thicker
Solution Approach 1:
The patent resolves the space-sensitivity tradeoff by changing the geometric arrangement from a vertical stacking configuration to a planar array configuration with skew angle. This dimensional reorganization allows sensors to be spaced optimally for sensitivity while maintaining a slim head profile through optimized lateral positioning rather than vertical stacking
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 enhances sensitivity and allows for higher areal density storage by maintaining a slim profile and reducing sensor spacing, enabling accurate data extraction from tracks with tighter pitches, including those below 50 nm, thus supporting high-density magnetic recording.
Implementation Method 1
a back side antiferromagnetic (AFM) layer positioned behind the lower free layer in an element height direction
Implementation Method 2
Magnetoresistive effect type magnetic heads are employed as sensors for reading magnetic information
Implementation Method 3
One such magnetoresistive effect type read head uses a giant magnetoresistive (GMR) effect in a multi-layered film formed by laminating a ferromagnetic metal layer on a non-magnetic intermediate layer
Data Source
AI summary
According to one embodiment, a magnetic head includes a lower magnetic shield positioned at a media facing surface of the head, a lower sensor positioned above the lower magnetic shield, the lower sensor including a lower free layer, a middle magnetic shield positioned above the lower sensor at the media facing surface of the head, and a back side antiferromagnetic (AFM) layer positioned behind the lower free layer in an element height direction, the back side AFM layer being configured to provide magnetic stabilization for the middle magnetic shield. In another embodiment, a method includes forming a lower sensor including a lower free layer, forming a back side AFM layer behind the lower free layer in an element height direction, and forming a middle magnetic shield above the lower sensor, wherein the back side AFM layer is configured to provide magnetic stabilization for the middle magnetic shield.