Magnetic Head Write Shield with Dual-Layer Return Path for Leakage Field Control
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Solution Overview
Problem
Magnetic heads for perpendicular magnetic recording systems face issues with unwanted erasure due to skew, which occurs when signals on adjacent tracks are erased or attenuated during writing, primarily caused by leakage magnetic fields from trailing shields with multiple crystal growth directions and defects.
Innovation Solution
The magnetic head design includes a write shield with a first return path section composed of two magnetic materials separated by an intermediate film, where the first portion is interposed between the medium facing surface and the coil's front end face, and the second portion is farther from the surface, ensuring uniform crystal growth and reducing grain boundaries, thereby minimizing leakage fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a write shield with trailing shield is provided to prevent leakage magnetic fields, then unwanted erasure is reduced, but crystal growth defects and grain boundaries occur causing leakage fields
Solution Approach 1:
The write shield is divided into a first shield layer and a second shield layer with different orientations. The first shield layer has a magnetization direction substantially perpendicular to the medium facing surface, while the second shield layer has a magnetization direction substantially parallel to the medium facing surface. This segmentation allows each layer to address different components of leakage magnetic fields independently, improving overall shielding effectiveness while maintaining manufacturing feasibility.
Solution Approach 2:
Different portions of the write shield are given different magnetic properties and orientations. The first shield layer provides perpendicular magnetization for blocking radial leakage fields, while the second shield layer provides parallel magnetization for blocking axial leakage fields. This local differentiation of magnetic properties optimizes the shielding function at each location within the write shield structure.
2Productivity
If recording density is increased to improve storage capacity, then more data can be stored, but unwanted erasure due to skew becomes more severe
Solution Approach 1:
The write shield structure is designed in advance to counteract the harmful effects of skew before they can cause unwanted erasure. By providing both perpendicular and parallel magnetization components through the two-layer shield structure, the system preemptively blocks leakage magnetic fields that would otherwise erase adjacent tracks during high-density recording operations.
Solution Approach 2:
The write shield employs a composite structure with two distinct shield layers having different magnetization orientations. This composite approach combines the advantages of perpendicular magnetization (effective against radial leakage) and parallel magnetization (effective against axial leakage), creating a robust shielding system that maintains signal integrity at high recording densities.
3Reliability
If main pole thickness is decreased near the medium facing surface to prevent erasure, then adjacent track erasure is reduced, but write field strength is weakened
Solution Approach 1:
The write shield acts as an intermediary structure that compensates for the reduced write field strength caused by the thinned main pole. By effectively blocking leakage magnetic fields through its dual-layer configuration, the write shield prevents unwanted erasure without requiring the main pole to maintain its original thickness, thus allowing the main pole to be optimized for other performance parameters.
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 configuration prevents unwanted erasure by ensuring smooth magnetization rotation and domain wall displacement, maintaining signal integrity and achieving higher recording densities.
Implementation Method 1
The first return path section allows a magnetic flux to flow therefrom
Implementation Method 2
The write shield and the return path section have the function of capturing a magnetic flux that is produced from the end face of the main pole and spreads in directions other than a direction perpendicular to the plane of the recording medium, thereby preventing the magnetic flux from reaching the recording medium
Implementation Method 3
The main pole is configured to pass a magnetic flux corresponding to the magnetic field produced by the coil, and to produce a write magnetic field for use to write data on the recording medium by means of the perpendicular magnetic recording system
Data Source
AI summary
A magnetic head includes a coil, a main pole, a write shield, and a return path section. The coil includes a coil element located on the trailing side of the main pole. The coil element has a front end face facing toward the medium facing surface. The return path section includes a first portion, a second portion, and an intermediate film interposed between the first portion and the second portion. Part of the first portion is interposed between the medium facing surface and the front end face of the coil element. Part of the second portion is interposed between the first portion and the front end face of the coil element.