Perpendicular Magnetic Head Shield Design for Track Erase
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Solution Overview
Problem
Magnetic heads for perpendicular magnetic recording systems face challenges in reducing the length of the magnetic path through the main pole and trailing shield, which affects recording density and write characteristics due to skew-induced adjacent track erase.
Innovation Solution
Incorporating a magnetic head design with a first and second shield made of magnetic material, along with gap parts and return path sections made of nonmagnetic and magnetic materials respectively, to reduce the magnetic path length and enhance the rate of change in the magnetic flux produced from the main pole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the magnetic path length through the main pole and shield is reduced to improve recording density, then the rate of change in magnetic flux increases, but the device complexity increases due to additional shields and return path sections
Solution Approach 1:
The magnetic head is segmented into multiple functional components: main pole, first shield, second shield, first return path section, and second return path section. Each segment serves a specific purpose in controlling magnetic flux distribution, allowing the magnetic path to be optimized for recording density while maintaining manageable complexity through modular design
Solution Approach 2:
Different regions of the magnetic head are assigned different magnetic properties: the main pole and shields use magnetic materials to concentrate and direct flux, while gap parts use nonmagnetic materials to isolate flux paths. This local differentiation of material properties enables precise control of magnetic flux distribution to achieve high recording density
2Reliability
If shields are added to prevent skew-induced adjacent track erase, then adjacent track erase is reduced, but the magnetic path length increases
Solution Approach 1:
The first and second shields act as intermediary elements between the main pole and the recording medium. These shields intercept and redirect magnetic flux that would otherwise cause adjacent track erase, serving as mediators that protect against skew-induced interference while the return path sections provide controlled flux return routes
Solution Approach 2:
The shield structure extends the magnetic path in the vertical dimension (away from the medium facing surface) rather than only in the horizontal direction. By positioning shields at different heights and using return path sections to connect them, the design creates three-dimensional flux management that prevents adjacent track erase without excessively lengthening the horizontal magnetic path
3Reliability
If the magnetic head is positioned near the air outflow end to reduce skew, then adjacent track erase decreases, but the magnetic path length through main pole and shield increases
Solution Approach 1:
The return path sections extract the magnetic flux from the shields and guide it back to the main pole through controlled paths. This separation of flux generation (main pole) and flux return (return path sections) allows optimization of the write field region while managing the overall magnetic path length independently
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 effectively reduces the magnetic path length through the second shield and main pole, improving recording density and preventing skew-induced adjacent track erase, thereby enhancing write characteristics such as overwrite property.
Implementation Method 1
a coil that produces a magnetic field 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 a magnetic flux corresponding to the magnetic field produced by the coil 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 backward of the end face of the main pole along a direction of travel of the recording medium; a second 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
Data Source
AI summary
A magnetic head includes: a coil; a main pole; a first shield disposed backward of the main pole along a direction of travel of a recording medium; a first return path section connecting the first shield to the main pole; a second shield disposed forward of the main pole along the direction of travel of the recording medium; and a second return path section connecting the second shield to the main pole. An interface between the first return path section and the main pole has an end closest to a medium facing surface, and an interface between the second return path section and the main pole has an end closest to the medium facing surface, the latter being closer to the medium facing surface than the former. The second return path section includes a yoke layer located away from the medium facing surface and in contact with the main pole. The coil includes at least one coil element that passes between the second shield and the yoke layer.