Hot Seed Bilayer Reduces Gap Field in Magnetic Recording Heads
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Solution Overview
Problem
Magnetic recording heads face challenges in achieving high areal density and reliability due to increased gap fields, which can cause the field generation layer of a spin torque oscillator to precess in the shunting direction, making it difficult to write smaller magnetic bit sizes without compromising downtrack effective field gradient.
Innovation Solution
A magnetic recording head design featuring a main pole, trailing shield, and a hot seed bilayer with a high magnetic moment material at the media facing surface and a low magnetic moment material recessed from the surface, along with a spin torque oscillator, to manage the gap field and enhance the field gradient and bit per inch capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the thickness of the trailing gap is increased to reduce the gap field, then the gap field is reduced, but the downtrack effective field gradient is reduced
Solution Approach 1:
The patent applies local quality by creating a wedge-shaped trailing gap where the gap thickness varies spatially - thinner at the media-facing edge and thicker at the rear. This non-uniform thickness distribution allows the gap field to be reduced at the critical media interface while maintaining sufficient downtrack field gradient for effective writing. The local variation in gap dimensions enables simultaneous optimization of both parameters that would be conflicting in a uniform gap design.
Solution Approach 2:
The trailing gap is designed with asymmetric geometry - the wedge shape creates an uneven distribution of magnetic field lines through the gap. The asymmetry in gap thickness allows different functional requirements to be met at different locations: the thinner front portion reduces gap field for better perpendicular recording, while the thicker rear portion maintains field gradient for adequate write capability. This asymmetric design resolves the contradiction by allowing the gap structure to perform multiple functions at different spatial locations.
2Object-affected harmful factors
If the trailing gap is made wedge-shaped to reduce gap field, then the gap field is reduced, but the manufacturing difficulty increases
Solution Approach 1:
The wedge-shaped trailing gap is formed as an integral part of the main pole piece during the initial fabrication process, before final assembly. This preliminary formation of the non-uniform gap structure simplifies manufacturing by avoiding the need for complex post-processing or separate assembly steps to create the wedge geometry. The gap profile is established early in the manufacturing sequence when the workpiece is still in a form amenable to shaping.
Solution Approach 2:
The patent utilizes parameter changes in the gap thickness dimension to achieve the wedge shape. By controlling the thickness parameter to vary continuously or in steps from front to rear of the trailing gap, the design achieves gap field reduction while maintaining manufacturability through standard fabrication techniques that can produce graded or stepped thickness profiles. This parameter variation approach is more manufacturable than attempting to create complex three-dimensional gap geometries.
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 reduces the gap field, increases the field gradient angle, and improves bit per inch capabilities, allowing for smaller trailing gaps without sacrificing performance, thus enabling more efficient data storage.
Implementation Method 1
The hot seed bilayer comprises a first layer comprised of a high magnetic moment material disposed at the media facing surface and a second layer comprised of a low magnetic material recessed from the media facing surface
Implementation Method 2
A spin torque oscillator is disposed between the main pole and the trailing shield at a media facing surface
Data Source
AI summary
The present disclosure generally relates to data storage devices, and more specifically, to a magnetic media drive employing a magnetic recording head. A magnetic recording head comprises a main pole disposed between a leading shield and a trailing shield. A spin torque oscillator is disposed between the main pole and the trailing shield at a media facing surface. A hot seed bilayer is disposed between the spin torque oscillator and the trailing shield, where the hot seed bilayer is conformal with the spin torque oscillator. The hot seed bilayer comprises a first layer comprised of a high magnetic moment material disposed at the media facing surface and a second layer comprised of a low magnetic material recessed from the media facing surface.