Non-Uniform Coil Thickness for Magnetic Recording Head
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Solution Overview
Problem
High data rates in hard disk drives require rapid directional and magnitude changes of the magnetic flux, leading to issues such as writer-induced writer protrusion (WIWP), which causes data erasure, poorly written bits, and damage to the magnetic recording head due to excessive heat and uncontrollable magnetization switching.
Innovation Solution
A writer coil with a thinner segment proximal to the write pole and a thicker segment distal to the write pole, allowing for increased magnetic field magnitude and faster magnetization switching without the need for large overshoot currents, while effective heat dissipation reduces WIWP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a uniform thickness writer coil is used, then the coil structure is simple and easy to manufacture, but the magnetic field magnitude near the write pole is insufficient and heat dissipation is poor
Solution Approach 1:
The writer coil is designed with non-uniform thickness where the first segment near the write pole has a first thickness and the second segment away from the write pole has a second thickness greater than the first thickness. This local differentiation optimizes heat dissipation in the distal region while maintaining magnetic field strength near the write pole, resolving the contradiction between heat dissipation performance and structural simplicity.
2Temperature
If a thicker writer coil is used, then heat dissipation is improved, but the magnetic field magnitude near the write pole decreases and magnetization switching speed reduces
Solution Approach 1:
By making the first segment thinner than the second segment, the coil maintains high magnetic field magnitude near the write pole (enabling fast magnetization switching) while the thicker second segment provides effective heat dissipation. This local differentiation resolves the contradiction between heat dissipation and magnetization switching speed.
Solution Approach 2:
The writer coil is divided into two distinct segments with different thicknesses: a first segment proximal to the write pole and a second segment distal to it. This segmentation allows each portion to perform its optimized function - the thinner first segment for magnetic field generation and the thicker second segment for heat dissipation - thereby resolving the contradiction between these two performance requirements.
3Speed
If a larger overshoot current is applied to achieve faster magnetization switching, then switching speed improves, but heat generation increases and writer-induced writer protrusion occurs
Solution Approach 1:
The non-uniform coil thickness design allows the first segment near the write pole to be thinner, which maintains high magnetic field magnitude and enables fast magnetization switching without requiring large overshoot currents. This eliminates the harmful thermal effects and writer-induced protrusion that would result from applying large currents, thus resolving the contradiction between switching speed and harmful thermal effects.
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 enables faster magnetization switching and reduced heat generation, minimizing WIWP and improving data integrity and bit size consistency without increasing the magnetic field's impact on the write pole.
Implementation Method 1
Current may be passed through the writer coil to generate a magnetic field through induction
Implementation Method 2
The write pole and return pole(s) may include magnetic materials with properties (e.g., high magnetic permeability, low magnetic coercivity) that enable them to guide flux of a generated magnetic field
Data Source
AI summary
A magnetic recording head includes a write pole including an end proximal to a media-facing surface of the magnetic recording head, a return pole disposed a distance from the write pole in a down-track dimension of the magnetic recording head, and a writer coil configured to produce a magnetic flux in the write pole. The writer coil includes a first segment and a second segment. The first segment is disposed proximal to the end of the write pole and between the write pole and the return pole. The second segment is electrically coupled to the first segment. A thickness of the second segment in the down-track dimension is greater than a thickness of the first segment in the down-track dimension.