Magnetoresistive Head with Longitudinal Biasing Layer Step
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Solution Overview
Problem
Current magnetoresistive heads with CPP structures face challenges in achieving high recording density due to limitations in read track width accuracy, stability, and signal-to-noise ratio, primarily caused by the high aspect ratio of lift-off mask materials and the shortening of stripe height, which affects magnetic anisotropy and thermal stability of the longitudinal biasing layer.
Innovation Solution
A magnetoresistive head design featuring a magnetoresistive sensor film with a stack including a pinning layer, first and second ferromagnetic layers, and a longitudinal biasing layer, where the longitudinal biasing layer has a longer length in the stripe height direction than the second ferromagnetic layer, and a surface step to increase thickness at the air bearing surface, ensuring improved magnetic field stability and reduced side reading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the pattern width of the lift-off mask material is narrowed to form a narrow read track width, then the read track width is reduced, but the pattern accuracy is lowered due to high aspect ratio causing bending and collapse
Solution Approach 1:
The longitudinal biasing layer is segmented into multiple sections along the stripe height direction, with each section having different thickness. This segmentation allows the mask pattern to be formed more easily while maintaining the required read track width, as the segmented structure reduces the effective aspect ratio that causes bending and collapse.
Solution Approach 2:
The longitudinal biasing layer is designed with non-uniform thickness distribution, where the thickness varies along the stripe height direction. This local quality variation enables the structure to maintain stability while achieving narrow read track width, as the thicker portions provide structural support while thinner portions achieve the desired dimensional precision.
2Length of moving object
If the stripe height is shortened to narrow the read track width, then the read track width is reduced, but the longitudinal biasing layer becomes more subject to thermal fluctuations
Solution Approach 1:
Instead of solely relying on stripe height to define read track width, the invention introduces thickness variation along the stripe height direction as an additional dimensional control parameter. The longitudinal biasing layer's thickness is modulated to compensate for the shortened stripe height, providing thermal stability through increased material volume in critical regions while maintaining narrow read track width.
Solution Approach 2:
The magnetoresistive head employs a composite structure combining the magnetoresistive sensor film with the longitudinal biasing layer of varying thickness. This composite design allows the thicker sections of the biasing layer to provide thermal stability while the overall structure maintains the narrow read track width required for high recording density.
3Length of moving object
If the stripe height is shortened to achieve narrow read track width, then the read track width is reduced, but the magnetic anisotropy is affected and read performance stability deteriorates
Solution Approach 1:
The invention changes the thickness parameter of the longitudinal biasing layer along the stripe height direction to compensate for the shortened stripe height. By adjusting this parameter, the magnetic anisotropy is maintained at appropriate levels, ensuring stable read performance while achieving the narrow read track width necessary for high recording density.
4Object-generated harmful factors
If the longitudinal biasing layer thickness is increased at the air bearing surface section, then side reading is suppressed, but the device complexity increases due to the step structure
Solution Approach 1:
The longitudinal biasing layer is designed with local quality variation, where only specific sections along the stripe height direction have increased thickness. The air bearing surface section has greater thickness to suppress side reading, while other sections maintain original thickness. This localized modification minimizes overall structural complexity while achieving the desired suppression of side reading effects.
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 performance stability, suppresses side reading, and allows for high-yield manufacturing with accurate geometric dimensions, improving signal-to-noise ratio and recording density.
Implementation Method 1
magnetoresistive sensor film which detects a change in a resistance in response to a change of an external magnetic field
Implementation Method 2
longitudinal biasing layer being disposed at each side of the magnetoresistive sensor film via an insulator film for insulation in a track width direction
Data Source
AI summary
According to one embodiment, a CPP structure magnetoresistive head includes a magnetoresistive sensor film between a lower shield layer and an upper shield layer and a longitudinal biasing layer disposed at each side of the magnetoresistive sensor film via a read track width defining insulator film. In the stripe height direction, the length of the longitudinal biasing layer is longer than the length of a second ferromagnetic layer in which its magnetization rotates in response to the external magnetic field. The second ferromagnetic layer is one of the layers comprising the magnetoresistive sensor film. At a stripe height, the surface of each longitudinal biasing layer has a step to change the thickness thereof across the step so that the air bearing surface section thereof has a larger thickness than any other section. Other structures using a magnetoresistive head and methods of production thereof are described as well.