AC Bias Current Write Field Enhancement in Magnetic Storage
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Solution Overview
Problem
The switching time of the write pole in magnetic storage systems, such as hard disk drives, is a limiting factor for high data rates due to the slow intrinsic time-constant of magnetization reversal, requiring additional power for magnetization reversal and overshoot, which increases power consumption and affects reliability.
Innovation Solution
The use of an AC bias current with a specific duty cycle and timing relative to the write current, applied to a write-field-enhancing structure within the write gap, improves switching speed without increasing power consumption, by optimizing the driving current's amplitude, duration, and timing to enhance the write field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If additional overshoot of write current is used to aid magnetization reversal, then switching time is improved, but power consumption increases
Solution Approach 1:
The patent applies periodic AC bias current to the write pole to assist magnetization reversal. The AC current oscillates at a frequency that resonates with the magnetic grains in the recording layer, enabling efficient switching without requiring excessive DC current overshoot. This periodic action reduces the total power consumption while achieving the required switching time performance.
Solution Approach 2:
The patent changes the parameter of write current from pure DC with overshoot to a composite waveform including AC bias current. By adjusting the frequency, amplitude, and phase of the AC component, the system optimizes magnetization reversal efficiency. This parameter change allows achieving faster switching times without increasing overall power consumption, as the AC component provides resonant assistance to the reversal process.
2Productivity
If higher data rates are implemented, then productivity is improved, but switching time requirements become more stringent and difficult to meet
Solution Approach 1:
The patent utilizes magnetic vibration through AC bias current applied to the write pole. The oscillating current creates a vibrating magnetic field that resonates with the magnetic grains in the recording layer, significantly reducing the switching time required. This vibration mechanism enables the write head to switch magnetization states rapidly, meeting the stringent timing requirements of high data rate applications.
Solution Approach 2:
The AC bias current mechanism serves multiple functions simultaneously: it assists magnetization reversal, reduces switching time, and enables high data rate operation without requiring separate optimization for each function. The same AC bias current that reduces switching time also enables the system to sustain higher data rates, making the solution universally applicable across multiple performance dimensions.
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 reduces switching time and improves write head performance while maintaining or reducing power levels, thereby enhancing reliability and durability.
Implementation Method 1
a write coil configured to magnetize the main pole
Implementation Method 2
The STO generates a high-frequency auxiliary field to the recording layer. Ideally, the auxiliary field has a frequency close to the resonance frequency of the magnetic grains in the recording layer to facilitate the switching of the magnetization of the grains.
Implementation Method 3
the auxiliary field has a frequency close to the resonance frequency of the magnetic grains in the recording layer to facilitate the switching of the magnetization of the grains
Implementation Method 4
a driving current control circuit configured to supply a driving current to the write-field-enhancing structure, wherein the driving current comprises an AC component
Data Source
AI summary
An apparatus comprises a main pole, a trailing shield, a write-field-enhancing structure, a write coil, a write current control circuit configured to supply a write current to the write coil to record a bit to a magnetic medium, and a driving current control circuit configured to supply a driving current to the write-field-enhancing structure, wherein the driving current comprises a driving pulse, and wherein the driving current comprises an AC component with a duty cycle selected based at least in part on a power constraint. A method of writing to a magnetic medium comprises supplying a write current to a write coil of a magnetic write head, and supplying a driving current to a free layer disposed in a write gap between a main pole and a trailing shield, wherein the driving current comprises an AC component with a duty cycle based at least in part on a power constraint.