Write Head Asymmetric Current for Magnetic Disk Bit Alignment
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Solution Overview
Problem
Magnetic disk devices face challenges in accurately writing data due to the easy and hard directions of magnetization in the cross-track direction, leading to potential misalignment of recording bits and variations in track pitch, which affect track density and bit error rate.
Innovation Solution
A magnetic disk device that outputs a recording current with differing magnitudes for positive and negative polarities to the write head, utilizing a magnetic field in the magnetization direction of the side shields to control the recording magnetic field, allowing for precise alignment and adjustment of recording bits and track pitch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a recording current with identical positive and negative amplitudes is applied to the write head, then the write head generates a recording magnetic field, but the magnetic flux flows unevenly in the easy and hard directions of magnetization in the side shields, causing misalignment of recording bits and variations in track pitch
Solution Approach 1:
The patent applies asymmetry by setting different amplitudes for positive and negative recording currents. Specifically, when the side shields are magnetized in a first direction, the positive recording current has a first amplitude and the negative recording current has a second amplitude that is different from the first amplitude. This asymmetric current application compensates for the unequal magnetic flux flow in the easy and hard directions of magnetization, thereby aligning recording bits accurately and maintaining consistent track pitch.
Solution Approach 2:
The patent changes the parameter of recording current amplitude based on the magnetization direction of the side shields. The controller adjusts the amplitude of recording currents according to the magnetization state, switching between different amplitude configurations to optimize magnetic flux distribution and ensure precise recording bit alignment regardless of the side shields' magnetization orientation.
2Manufacturing precision
If the magnetic flux flows easily in one direction and hardly flows in the other direction in the side shields, then magnetization is achieved, but track density varies and bit error rate increases
Solution Approach 1:
The patent uses asymmetry in recording current amplitudes to counterbalance the asymmetric magnetic flux flow characteristics of the side shields. By applying a larger amplitude current in the direction where magnetic flux flows harder and a smaller amplitude current where magnetic flux flows easily, the patent achieves uniform magnetic field distribution, consistent track pitch, and uniform track density across the recording medium.
Solution Approach 2:
The patent dynamically adjusts recording current parameters based on the magnetization state of the side shields. When the side shields are magnetized in different directions, the controller changes the amplitude configuration of the recording currents to maintain optimal magnetic flux flow, thereby ensuring consistent track pitch and uniform track density throughout the recording process.
3Ease of operation
If identical amplitudes are used for positive and negative recording currents, then the write processing is simplified, but recording quality deteriorates due to misalignment and track pitch variation
Solution Approach 1:
The patent implements dynamic adjustment of recording current amplitudes based on the magnetization direction of the side shields. The controller automatically selects between different amplitude configurations (first amplitude for positive/negative currents, or second amplitude for positive/negative currents) according to the real-time magnetization state, maintaining both operational simplicity through automated control and high recording precision through adaptive parameter adjustment.
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 approach improves track density and reduces bit error rates by enabling precise control over recording bit alignment and track pitch, enhancing recording quality and capacity.
Implementation Method 1
a recording current is applied to the write head, whereby a recording magnetic field is excited
Implementation Method 2
The side shields are magnetized in one direction in the cross-track direction. For this reason, in the write head, an easy direction of magnetization in which the magnetic flux of the recording magnetic field can easily flow, and a hard direction of magnetization in which the magnetic flux of the recording magnetic field can hardly flow exist in the cross-track direction
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk, a head including a main pole configured to apply a recording magnetic field to the disk, and side shields provided in a first direction with respect to the main pole and possessing a magnetic field in the magnetization direction of the first direction, and a controller configured to output a recording current in which a magnitude of a first electric current and a magnitude of a second electric current opposite to the first electric current in direction of the current are different from each other to the head according to the magnetic field of the side shields.