Multi-sensor Reader With Oppositely Biased Sensing Layers
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Solution Overview
Problem
Magnetic data storage devices face challenges with neighboring track interference, leading to readback errors and lower areal density capabilities due to the magnetic fields from adjacent tracks affecting the sensing layers of read sensors.
Innovation Solution
A multi-sensor reader is designed with first and second read sensors, each having a sensing layer with magnetization that changes in response to an external magnetic field, but biased in opposite directions, using magnetic structures such as shield pinned layers and antiferromagnetically coupled layers to reduce interference from neighboring tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single read sensor is used to read magnetic data, then the device structure is simple, but neighboring track interference causes readback errors and reduces measurement precision
Solution Approach 1:
The read sensor is divided into multiple sensing elements (first read sensor and second read sensor) with different bias directions. Each element reads data from adjacent tracks, and the signals are combined to eliminate neighboring track interference, thereby improving measurement precision while managing device complexity through functional segmentation.
Solution Approach 2:
The patent uses sensing elements with opposite bias directions (one biased in the first direction, another in the opposite second direction). By inverting the bias direction of adjacent sensing elements, the neighboring track interference affects each element differently, allowing the interference to be cancelled out when signals are combined, thus improving readback accuracy.
2Reliability
If multiple read sensors with opposite bias directions are used, then neighboring track interference is reduced, but the device complexity increases
Solution Approach 1:
The reader is segmented into multiple sensing elements with different bias orientations. Each element is responsible for reading data with reduced interference from specific neighboring tracks, improving reliability by eliminating readback errors while distributing the complexity across multiple specialized components rather than one complex sensor.
Solution Approach 2:
Multiple sensing elements with opposite bias directions are combined in a single reader assembly. The signals from these elements are processed and combined to cancel out neighboring track interference, achieving improved reliability (lower bit error rates) while managing complexity through integrated signal processing of the combined elements.
3Manufacturing precision
If traditional single-sensor configuration is used, then manufacturing is simpler, but areal density capabilities are limited due to interference
Solution Approach 1:
The sensor stack is segmented into multiple reading elements with different bias directions, allowing each element to operate with reduced interference. This segmentation enables higher areal density capabilities by allowing closer track spacing without excessive interference, while manufacturing processes are adapted to fabricate these segmented structures using established thin-film deposition techniques.
Solution Approach 2:
The bias direction parameter is changed for different sensing elements within the same reader assembly. By varying the bias direction parameter (first direction vs. opposite second direction), the patent enables differential response to neighboring track fields, improving areal density capabilities while using standard manufacturing processes to create the varied parameter configuration.
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 reduces interference from neighboring tracks by half, resulting in lower bit error rates and increased areal density capabilities by allowing the sensing layers to effectively read data without interference from adjacent tracks.
Implementation Method 1
a magnetoresistive (MR) sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor may be employed as the read transducer to read a magnetic signal from the magnetic media. The MR sensor has an electrical resistance that changes in response to an external magnetic field.
Implementation Method 2
The first biasing component includes a first magnetic structure comprising a shield pinned layer having a magnetization that is pinned by an antiferromagnetic layer.
Implementation Method 3
a first biasing component configured to magnetically bias the sensing layer of the first sensor stack in a first direction. The second read sensor includes a second sensor stack including a sensing layer having a magnetization that changes according to an external magnetic field, and a second biasing component configured to magnetically bias the sensing layer of the second sensor stack in a second direction that is substantially opposite the first direction.
Data Source
AI summary
A multi-sensor reader includes first and second read sensors. The first read sensor includes a first sensor stack including a sensing layer having a magnetization that changes according to an external magnetic field, and a first biasing component configured to magnetically bias the sensing layer of the first sensor stack in a first direction. The second read sensor includes a second sensor stack including a sensing layer having a magnetization that changes according to an external magnetic field, and a second biasing component configured to magnetically bias the sensing layer of the second sensor stack in a second direction that is substantially opposite the first direction.