TMR Sensor Scissor Design for Resolution
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Solution Overview
Problem
Scissor type sensors in magnetoresistive devices face challenges with strong magnetic coupling between shields and free ferromagnetic layers, leading to decreased resolution and increased magnetic read gap due to detection of extraneous recording bits, limiting their practical application.
Innovation Solution
A TMR and CPP-GMR read head design is implemented, featuring a specific layered structure including a bottom magnetic shield, non-magnetic seed layers, an antiferromagnetic layer, coupling layers, and free magnetic layers, with magnetic side shields and a soft bias layer to achieve a scissor magnetic configuration, reducing noise and improving resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scissor type sensors are used to improve sensitivity, then sensitivity is improved, but resolution decreases due to detection of extraneous recording bits
Solution Approach 1:
The sensor is divided into two separate free magnetic layers (first free magnetic layer and second free magnetic layer) with different magnetization orientations. Each layer detects different magnetic field components, allowing the sensor to distinguish between the target recording bit and extraneous bits, thereby maintaining high sensitivity while improving resolution.
Solution Approach 2:
The first free magnetic layer is configured with in-plane magnetization to detect magnetic fields along one direction, while the second free magnetic layer is configured with perpendicular magnetization to detect magnetic fields along a different direction. This local differentiation in magnetic properties enables selective detection and improves resolution by filtering out extraneous signals.
2Reliability
If strong magnetic coupling between shields and free ferromagnetic layers is used to improve sensitivity, then sensitivity is improved, but magnetic read gap increases
Solution Approach 1:
The invention transitions from a single-layer sensor detecting in-plane magnetic fields to a multi-layer sensor structure that detects perpendicular magnetic fields. By changing the detection dimension from in-plane to perpendicular magnetization, the sensor achieves strong coupling with the magnetic recording medium while maintaining a smaller magnetic read gap, thus improving both sensitivity and resolution.
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
The design enhances read resolution by minimizing the magnetic read gap and improving recording density, effectively isolating stray magnetic fields from non-target bits, thereby increasing the precision of data reading.
Implementation Method 1
an antiferromagnetic layer (AFM), a coupling layer, a first free magnetic layer... the FL1 receives a bias field from the AFM in the track width + direction
Implementation Method 2
A pair of magnetic side shield layers is positioned on respective sides of the second free magnetic layer... the FL2 receives a bias field from the pair of magnetic shields in the track width − direction
Implementation Method 3
A soft bias layer is positioned behind the first free magnetic layer (FL1) and the second free magnetic layer (FL2)... in order to give both FL1 and FL2 a bias magnetic field in the stripe height direction
Implementation Method 4
A TMR (tunnel magnetoresistance) and CPP-GMR (current perpendicular to plane giant magnetoresistive) read head is provided
Implementation Method 5
A TMR (tunnel magnetoresistance) and CPP-GMR (current perpendicular to plane giant magnetoresistive) read head is provided
Data Source
AI summary
A read head is provided with a scissors sensor. The read head may include a bottom magnetic shield, and a first non-magnetic seed layer, a magnetic seed layer, a second non-magnetic seed layer, an antiferromagnetic layer, a coupling layer, a first free magnetic layer, a spacer layer, and a second free magnetic layer positioned above the bottom magnetic shield, in this order. A pair of magnetic side shield layers may be positioned on respective sides of the second free magnetic layer.