Adjustable Biasing for Magnetoresistive Sensor Soft Error Reduction
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Solution Overview
Problem
Conventional magnetoresistive sensors face challenges in maintaining consistent soft error rates (SER) due to variations in sensor dimensions and magnetic properties as they decrease in size, leading to increased thermomagnetic noise and higher SER rates, making it difficult to manufacture sensors with identical dimensions and magnetic properties.
Innovation Solution
A magnetoresistive sensing system with adjustable biasing circuitry that adjusts the relative magnetizations of ferromagnetic layers in CPP-MR read heads after manufacturing, using a bias-adjusting magnetic field to improve sensitivity and reduce SER by changing the angle between magnetization vectors, thereby enhancing the read head's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sensor size is decreased to increase data density, then productivity is improved, but soft error rate increases due to increased thermomagnetic noise
Solution Approach 1:
The patent changes the magnetic field parameter by introducing a bias-adjusting magnetic field that can modify the relative magnetization angles of ferromagnetic layers. This allows optimization of sensor sensitivity and reduction of soft error rates even as sensor dimensions decrease, thereby maintaining reliability while improving data density.
Solution Approach 2:
The patent introduces adjustable biasing circuitry that can dynamically adjust the bias magnetic field after manufacturing. This dynamic adjustment capability allows each sensor to be individually optimized to compensate for manufacturing variations and size-related effects, reducing soft error rates without sacrificing the benefits of smaller sensor sizes.
2Reliability
If sensor dimensions and magnetic properties are made identical through precise manufacturing, then soft error rate is reduced, but manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The patent enables sensors to self-adjust their performance characteristics through post-manufacturing calibration. The adjustable biasing circuitry allows each sensor to be individually tuned to achieve optimal performance, compensating for manufacturing variations without requiring extremely tight manufacturing tolerances.
Solution Approach 2:
The patent introduces adjustable magnetic field parameters that can be modified after manufacturing to compensate for dimensional and magnetic property variations. This allows sensors with slightly different manufacturing characteristics to still achieve consistent low soft error rates through parameter optimization.
3Reliability
If adjustable biasing circuitry is added to reduce soft error rate, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines the biasing function with existing sensor structures by integrating adjustable biasing circuitry that works with the ferromagnetic layers. The bias-adjusting magnetic field is generated within the existing sensor architecture, merging the reliability-improving function with the read head structure rather than adding completely separate systems.
4Adaptability or versatility
If post-manufacturing adjustment is implemented, then adaptability is improved, but ease of manufacture decreases
Solution Approach 1:
The patent implements preliminary characterization and adjustment procedures that are performed once during manufacturing or initialization. The adjustable biasing circuitry is configured to allow post-manufacturing adjustment, but the adjustment process itself is designed to be performed as a preliminary calibration step rather than requiring continuous complex intervention.
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 system effectively reduces the soft error rate by adjusting the bias of ferromagnetic layers, improving the sensitivity of the read heads and ensuring they operate within acceptable limits, even after manufacturing and installation in disk drives.
Implementation Method 1
a bias-adjusting magnetic field that acts on one or more of the ferromagnetic layers to change the relative magnetizations
Implementation Method 2
a giant magnetoresistance (GMR) effect
Implementation Method 3
the rotation of the free-layer magnetization relative to the reference-layer magnetization due to the presence of an external magnetic field is detectable as a change in electrical resistance
Implementation Method 4
the current tunneling perpendicularly through the layers depends on the relative orientation of the magnetizations in the two ferromagnetic layers
Data Source
AI summary
A magnetoresistive sensing system includes a current-perpendicular-to-the-plane magnetoresistive (CPP-MR) read head and adjustable biasing circuitry connected to the read head for adjusting the relative magnetizations of one or more of the ferromagnetic layers in the read head. The biasing circuitry generates a bias current in the read head that generates a bias-adjusting magnetic field that acts on one or more of the ferromagnetic layers. For a conventional read head, the bias-adjusting field acts orthogonal to the field from the reference layer to change the angle between the magnetization of the free layer and the magnetization of the reference layer. For a scissoring-type read head, the bias-adjusting field acts parallel to the transverse bias field to change the angle between the magnetizations of the two free layers. This results in an improvement in the sensitivity of the read head to bring the soft error rate (SER) below an acceptable level.