Spin Torque Oscillator Bias Control for Magnetic Disk Recording
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Solution Overview
Problem
In magnetic disk devices using perpendicular magnetic recording, high-frequency oscillators experience instability at high sampling frequencies, leading to deteriorated signal quality and recording density due to insufficient oscillation responsiveness, which interferes with adjacent tracks.
Innovation Solution
A magnetic disk device with a recording head that includes a spin torque oscillator (STO) and a bias voltage control system, where the STO bias voltage is dynamically adjusted based on data sampling frequency and radial position to optimize oscillation and reduce interference with adjacent tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sampling frequency of recording data is increased to improve recording density, then the recording capacity increases, but the oscillation responsiveness of the high-frequency oscillator becomes insufficient causing unstable oscillation and interference with adjacent tracks
Solution Approach 1:
The patent applies dynamics by making the bias voltage adjustable and variable rather than fixed. The bias voltage applied to the spin torque oscillator is dynamically changed based on the data sampling frequency, allowing the oscillator to maintain stable operation across different recording conditions and frequencies.
Solution Approach 2:
The patent implements parameter changes by varying the bias voltage parameter according to the sampling frequency. Different bias voltage values are applied depending on the recording data frequency, optimizing the oscillator's performance for each specific frequency range and preventing adjacent track interference.
2Device complexity
If a fixed bias voltage is applied to the high-frequency oscillator, then the device structure remains simple, but the oscillation responsiveness deteriorates at high sampling frequencies causing signal quality degradation
Solution Approach 1:
The patent transitions from a static bias voltage system to a dynamic one where the bias voltage can be adjusted based on operating conditions. This dynamic control enables the system to adapt to high sampling frequencies while maintaining signal quality, despite the increased structural complexity.
Solution Approach 2:
The patent changes the bias voltage parameter according to the sampling frequency requirements. By implementing variable bias voltage control, the system achieves high signal quality across different frequency ranges while managing the complexity through structured voltage adjustment mechanisms.
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
The dynamic adjustment of STO bias voltage improves signal quality and recording density by reducing oscillation-induced interference, maintaining stable oscillation even at high sampling frequencies and enhancing recording performance.
Implementation Method 1
a spin torque oscillator (STO) in the write gap
Implementation Method 2
a main magnetic pole that generates a magnetic field in the perpendicular direction
Implementation Method 3
a return magnetic pole opposed to the main magnetic pole with a write gap therebetween to return magnetic flux from the main magnetic pole
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a magnetic disk, a recording head and a controller. The recording head includes a high-frequency oscillator disposed in a write gap between a main magnetic pole and a return magnetic pole and configured to oscillate in accordance with a bias voltage, and a bias voltage supply circuit configured to supply the bias voltage to the high-frequency oscillator. The controller includes a bias voltage controller configured to control the bias voltage to be applied to the high-frequency oscillator in accordance with a sampling frequency of data when the data is recorded on the magnetic disk by the recording head.