Perpendicular Magnetic Head Pole Shield Design
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Solution Overview
Problem
Magnetic heads for perpendicular magnetic recording face challenges in producing a sufficient write magnetic field while reducing the length of the magnetic path through the main pole and shield, leading to issues like adjacent track erasure due to skew and limited recording density.
Innovation Solution
A magnetic head design incorporating a first and second coil, a main pole, a first and second shield, and return path sections made of magnetic materials, with the first coil having fewer turns than the second coil to reduce the magnetic path length and enhance magnetomotive force, allowing the main pole to produce a sufficient write magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the magnetic path length through the main pole and shield is reduced to prevent adjacent track erasure, then recording density is improved, but the write magnetic field strength becomes insufficient
Solution Approach 1:
The magnetic head is divided into multiple functional segments: main pole for write field generation, shields for magnetic field confinement, return path sections for flux return, and excitation coils for magnetomotive force generation. Each segment is optimized independently to resolve the contradiction between short magnetic path and sufficient field strength
Solution Approach 2:
The return path sections are merged with the main pole and shields to form integrated magnetic circuits. This merging creates efficient flux paths that reduce overall magnetic path length while maintaining field strength through optimized magnetic coupling between components
Solution Approach 3:
The patent optimizes multiple parameters including the number of coil turns, coil winding density, magnetic material properties, and geometric dimensions of the main pole and shields. By changing these parameters, the magnetic path length is reduced while compensating for field strength through increased magnetomotive force from optimized coil configurations
2Manufacturing precision
If the main pole width is reduced to achieve higher recording density, then linear recording density is improved, but overwrite capability deteriorates
Solution Approach 1:
The main pole exhibits local quality variations with different widths at different locations: narrower width at the medium-facing end for high recording density, and wider base section for sufficient magnetomotive force and improved overwrite capability. This localized dimensional variation resolves the contradiction between density and reliability
Solution Approach 2:
The solution moves from a single-dimensional parameter (uniform pole width) to multi-dimensional optimization by varying the pole width in the vertical dimension (from base to tip) while maintaining narrow width at the recording surface. This dimensional approach allows simultaneous achievement of high density and good overwrite performance
3Ease of operation
If skew occurs during magnetic head movement, then positioning is achieved, but adjacent track erasure is caused
Solution Approach 1:
Shields are positioned in advance around the main pole to create a magnetic field confinement structure that prevents skew-induced field spread to adjacent tracks. This preliminary protective structure counteracts the harmful effects of skew before adjacent track erasure can occur
Solution Approach 2:
The shields, which might seem to increase device complexity, actually convert the potential harm of skew into a benefit by channeling and confining the magnetic field more effectively. The skew that would normally cause erasure is instead utilized to enhance field concentration within the intended track when properly guided by the shield geometry
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 design effectively prevents adjacent track erasure and improves recording density by allowing the main pole to produce a sufficient write magnetic field while reducing the magnetic path length, thereby enhancing write characteristics and recording capabilities.
Implementation Method 1
a first coil and a second coil that produce magnetic fields corresponding to data to be written on the recording medium
Implementation Method 2
a main pole that has an end face located in the medium facing surface, allows magnetic fluxes corresponding to the magnetic fields produced by the first and second coils to pass, and produces a write magnetic field for writing the data on the recording medium
Implementation Method 3
a first shield made of a magnetic material and having an end face that is located in the medium facing surface at a position forward of the end face of the main pole in a direction of travel of the recording medium
Data Source
AI summary
A magnetic head includes first and second coils, a main pole, a first shield, and first and second return path sections. The first shield and the first return path section are located forward of the main pole in the direction of travel of the recording medium. The first return path section connects the main pole and the first shield so that a first space is defined. The second return path section is located backward of the main pole in the direction of travel of the recording medium so that a second space is defined. The first coil includes at least one first coil element passing through the first space. The second coil includes a plurality of second coil elements passing through the second space. The at least one first coil element is smaller in number than the second coil elements.