Magnetic Head Soft Magnetic Layer Behind TMR Sensor
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Solution Overview
Problem
The miniaturization of magnetic recording components in HDDs leads to decreased sensor output and increased noise, making it difficult to read signals effectively at higher recording densities, as the sensor size is reduced.
Innovation Solution
A magnetic head design that includes a soft magnetic layer positioned behind the sensor, with a rear insulating layer between the soft magnetic layer and the sensor, and an antiferromagnetic or high-coercivity material to stabilize the magnetization free layer, allowing efficient rotation and maintaining stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the sensor size is reduced to accommodate higher recording densities, then the recording density increases, but the sensor output drops and noise increases
Solution Approach 1:
The patent introduces a soft magnetic layer positioned behind the sensor in the element height direction (perpendicular to the ABS), adding a new spatial dimension to the sensor structure. This allows the sensor to detect magnetic flux from both the front (ABS side) and back sides, effectively increasing the sensing area and output without increasing the lateral footprint, thus maintaining high recording density while improving sensor output.
Solution Approach 2:
The patent employs a composite structure combining the TMR sensor with a soft magnetic layer and insulating layers. The soft magnetic layer enhances the magnetic field detection capability, while the insulating layers provide electrical isolation. This composite structure improves sensor output and signal-to-noise ratio without requiring larger sensor dimensions, resolving the contradiction between recording density and sensor output.
2Quantity of substance
If the sensor size is reduced to accommodate higher recording densities, then the recording density increases, but noise increases
Solution Approach 1:
The patent introduces insulating layers as intermediary elements between the TMR sensor and the soft magnetic layer, and between the soft magnetic layer and the lower magnetic shield. These insulating layers provide electrical isolation that reduces noise coupling and interference, allowing the sensor to operate at higher recording densities with improved signal-to-noise ratio.
Solution Approach 2:
By adding the soft magnetic layer behind the sensor in the element height direction, the patent creates additional magnetic flux detection paths that enhance the signal strength. This dimensional addition improves the signal-to-noise ratio by increasing the useful signal detection capability without proportionally increasing noise, thus enabling higher recording densities.
3Reliability
If a soft magnetic layer is added behind the sensor to enhance output, then sensor output improves, but device complexity increases
Solution Approach 1:
The soft magnetic layer positioned behind the sensor serves multiple functions: it enhances magnetic flux detection to improve sensor output, provides magnetic shielding to reduce noise, and works in conjunction with the insulating layers to maintain electrical isolation. This multi-functionality allows the structure to improve sensor performance without requiring additional separate components, thus limiting the increase in device complexity.
Solution Approach 2:
The patent merges the soft magnetic layer with the existing sensor structure in the element height direction, integrating it as part of the overall sensor assembly. The insulating layers are positioned to simultaneously provide electrical isolation and structural support. This merging approach consolidates multiple functions into a unified structure, improving sensor output while minimizing the increase in device complexity.
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 enhances read sensor output while maintaining stability, improving recording density capabilities without compromising signal quality.
Implementation Method 1
tunneling magnetoresistance (TMR) films have come to be used in read sensors of HDDs, which has resulted in improved sensor performance (such as output, signal-to-noise ratio (SNR), etc.)
Implementation Method 2
The magnetization of the ferromagnetic layer is fixed by the exchange coupling magnetic field generated at the interface of the ferromagnetic layer and the antiferromagnetic layer
Implementation Method 3
a soft magnetic layer is arranged at a rear face of the TMR head on an opposite side to that of an ABS side. In this case, an external magnetic field is efficiently applied to a magnetization free layer of the TMR head due to arrangement of the soft magnetic layer on the rear face
Data Source
AI summary
A magnetic head according to one embodiment includes a read sensor adapted for sensing an external magnetic field; an upper magnetic shield positioned above the read sensor along an air bearing surface (ABS) of the read sensor; a lower magnetic shield positioned below the read sensor along the ABS of the read sensor; a rear insulating layer positioned on a rear side of the read sensor, the rear side being on an opposite side of the read sensor as the ABS of the read sensor; and a soft magnetic layer positioned near the rear side of the read sensor opposite the ABS of the read sensor, wherein the rear insulating layer is positioned between the soft magnetic layer and the read sensor, and wherein the rear insulating layer is positioned between the soft magnetic layer and the lower magnetic shield.