Dual Capping Layer for Magnetoresistive Sensor Noise Reduction
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Solution Overview
Problem
In magnetic read head sensors for hard disk drives, the increasing noise generated by thermal vibrations in the free magnetic layer limits the signal-to-noise ratio (SNR) as track widths narrow, necessitating a reduction in magnetic coupling to enhance domain control and biasing field.
Innovation Solution
A dual capping layer with a magnetic layer on a nonmagnetic layer is used to reduce magnetic coupling between the free magnetic layer and the upper shield, combined with a multilayer upper shield and a coil structure adjacent to the side shield to control and enhance the bias field, thereby improving domain control and SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If track width is narrowed to increase recording density, then recording density is improved, but magnetic noise increases proportionally reducing signal-to-noise ratio
Solution Approach 1:
A nonmagnetic layer is introduced as an intermediary between the free magnetic layer and the upper magnetic shield. This nonmagnetic layer acts as a mediator that reduces the magnetic coupling between these two components, thereby decreasing magnetic noise while preserving the benefits of narrow track width for high recording density
Solution Approach 2:
The upper shield is constructed as a composite magnetic structure with multiple layers including bottom and top magnetic layers separated by a nonmagnetic layer. This composite structure allows optimization of magnetic field generation while reducing unwanted magnetic coupling and noise
2Reliability
If magnetic coupling between free magnetic layer and upper shield is reduced, then domain control and bias field are enhanced, but sensor structure complexity increases
Solution Approach 1:
The upper magnetic shield is segmented into multiple layers (bottom magnetic layer, nonmagnetic layer, top magnetic layer) with distinct functions. This segmentation allows each layer to be optimized independently for its specific role in field generation and noise reduction
Solution Approach 2:
The nonmagnetic layer is extracted and placed between the free magnetic layer and upper shield to specifically address the magnetic coupling issue. This extracted component performs the dedicated function of reducing magnetic noise without interfering with other sensor operations
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 solution effectively reduces magnetic noise and increases domain controllability, enhancing the bias field and signal-to-noise ratio, enabling improved magnetic storage density and read resolution.
Implementation Method 1
dual capping layer including a magnetic layer disposed on a nonmagnetic layer... reduce magnetic coupling so as to enhance magnetic biasing field
Implementation Method 2
coil structure may be positioned adjacent to a side shield. The coil structure positioned adjacent to the side shield may effectively change and adjust the bias field generated to the sensor
Implementation Method 3
The read head sensor is a magnetoresistive effect type... By sensing the relative magnetizations of two ferromagnetic thin films, such as a free magnetic layer and a pinned magnetic layer, magnetic information can be read from nanoscale magnets on the disk
Data Source
AI summary
The present disclosure generally relates to a read head sensor in a magnetic recording head. The read head sensor comprises a dual capping layer in a sensor stack that may reduce magnetic coupling so as to enhance magnetic bias field, e.g., domain control, in the read head sensor. Furthermore, an upper shield with multiple film stack having different film properties may also be utilized to enhance bias field generated to the read head sensor. Additionally, a coil structure may be positioned adjacent to a side shield to enhance bias field generation in the read head sensor.