Perpendicular Magnetic Recording Head Gap Structure
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Solution Overview
Problem
Existing perpendicular magnetic recording heads suffer from increased noise and reduced signal-to-noise ratio due to the wide width of magnetization reversal between recording patterns, caused by the isotropic spreading of the recording magnetic field, which results in curved magnetic field lines on the trailing side of the recording patterns.
Innovation Solution
A perpendicular magnetic recording head design featuring a main magnet pole layer with a concave portion on the trailing side and a return yoke layer with a convex portion on the leading side, both formed to maintain a constant gap length, effectively approximating the magnetic field line on the trailing side to be parallel with the track width, thereby reducing the width of magnetization reversal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the recording magnetic field spreads isotropically from the main magnet pole layer, then the magnetic field can be applied to the recording medium, but the width of magnetization reversal increases and the signal-to-noise ratio deteriorates
Solution Approach 1:
The patent applies local quality by creating a non-uniform gap structure where the gap length varies in the track width direction. Specifically, the gap is shorter at the center portion and longer at the edge portions of the track width, which locally concentrates the magnetic field at the center and reduces isotropic spreading, thereby narrowing the magnetization reversal width and improving signal-to-noise ratio
Solution Approach 2:
The patent employs asymmetry by making the gap length asymmetric with respect to the track width direction. The gap structure is designed to have different gap lengths at different positions (shorter at center, longer at edges), which breaks the symmetric isotropic spreading pattern and creates a directed magnetic field distribution that reduces magnetization reversal width
2Loss of information
If the magnetic field line on the trailing side is curved, then the magnetic field is distributed over a wider area, but the reproduction output deteriorates and noise increases
Solution Approach 1:
The patent applies local quality by creating a non-uniform gap structure where the gap length varies in the track width direction. Specifically, the gap is shorter at the center portion and longer at the edge portions of the track width, which locally concentrates the magnetic field at the center and reduces isotropic spreading, thereby narrowing the magnetization reversal width and improving signal-to-noise ratio
Solution Approach 2:
The patent employs asymmetry by making the gap length asymmetric with respect to the track width direction. The gap structure is designed to have different gap lengths at different positions (shorter at center, longer at edges), which breaks the symmetric isotropic spreading pattern and creates a directed magnetic field distribution that reduces magnetization reversal width
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 improves the signal-to-noise ratio and output by reducing the width of magnetization reversal and preventing isotropic spreading of the recording magnetic field, leading to more accurate data reproduction with reduced noise.
Implementation Method 1
A recording magnetic field 4 is generated from the main magnet pole layer 1 toward the recording medium 3, and the recording magnetic field 4 passes through the recording layer 3c--> the intermediate layer 3b--> the soft layer 3a of the recording medium 3
Implementation Method 2
the end surface of the main magnet pole layer on the trailing side is depressed at the center in the direction of the width of the track on the trailing side... approximating the magnetic field line on the trailing side of the recording patterns to the direction parallel with the direction of the width of the track
Implementation Method 3
The perpendicular magnetic recording head provides the perpendicular magnetic field to the recording medium 3, and magnetizes the recording layer 3c of the recording medium 3 in the perpendicular direction
Implementation Method 4
the recording magnetic field 4 spreads isotropically from the main magnet pole layer 1 to the recording medium 3
Data Source
AI summary
A concave portion is formed on the end surface of a main magnet pole layer on the trailing side. A convex portion is formed on the end surface of a return yoke layer on the leading side, which opposes the concave portion formed on the end surface of the main magnet pole layer on the trailing side, and the distance (gap length) between the main magnet pole layer and the return yoke layer in the direction of the film thickness is constant. Consequently, the magnetic field generating from the main magnet pole layer toward the recording medium is appropriately prevented from isotropically spreading in the trailing direction, and the width of magnetization reversal between the recording patterns, which are magnetized reversely from each other, can be reduced over the entire area.