Spin Torque Oscillator Magnetic Head Phase Fluctuation Control
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Solution Overview
Problem
Magnetic recording apparatuses using magnetoresistive elements face challenges with shot noise and white noise, which reduce the signal-to-noise (S/N) ratio, and the application of a spin torque oscillator as a magnetic sensor is proposed to improve this ratio but results in increased bit error rate due to fluctuations in oscillation power when the relaxation rate is small.
Innovation Solution
A magnetic recording and reproducing apparatus is designed with a spin torque oscillator that includes a stacked film structure with ferromagnetic and non-magnetic layers, utilizing electrodes to induce precession of magnetization and output rotating magnetic fields, and a delay detection circuit to reduce phase fluctuations and control signal reproduction based on detected signal amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spin torque oscillator is applied as a magnetic sensor to improve S/N ratio, then the S/N ratio is improved, but the bit error rate increases due to oscillation power fluctuations when relaxation rate is small
Solution Approach 1:
The patent changes the operational parameters of the spin torque oscillator by controlling the write current amplitude and pulse width to regulate oscillation power. By adjusting these parameters, the system maintains stable oscillation power even when relaxation rate is small, thereby reducing bit error rate while preserving the high S/N ratio advantage
Solution Approach 2:
The patent implements feedback control by detecting the oscillation power of the spin torque oscillator and using this information to adjust subsequent write operations. The system monitors power fluctuations and compensates for them by modifying current parameters, ensuring reliable bit error rates while maintaining the improved S/N ratio
2Quantity of substance
If magnetoresistive elements are used in magnetic heads to improve recording density, then recording density is improved, but shot noise and white noise increase reducing S/N ratio
Solution Approach 1:
The patent replaces the conventional magnetoresistive sensing mechanism with a spin torque oscillator-based magnetic sensor. This substitution eliminates the shot noise and white noise inherent in magnetoresistive elements while maintaining high recording density capability, thereby achieving both high recording density and high S/N ratio
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 apparatus achieves a high S/N ratio by reducing phase fluctuations and controlling signal reproduction, maintaining a low bit error rate even when the oscillation power relaxation rate is small, thereby enhancing the reliability of bit information retrieval.
Implementation Method 1
a magnetic head having a spin torque oscillator configured to read out bit information which is recorded on a magnetic recording medium
Implementation Method 2
utilizing electrodes to induce precession of magnetization and output rotating magnetic fields
Implementation Method 3
With utilizing a magnetic head using a magnetoresistive element
Data Source
AI summary
A magnetic recording and reproducing apparatus for recording and reproducing bit information comprising a magnetic head having a spin torque oscillator configured to readout bit information which is recorded on a magnetic recording medium, a detector configured to detect amplitude of a first signal, the first signal which is to reproduce the bit information, and a controller configured to control the magnetic head so as to read the bit information recorded on the magnetic recording medium when the amplitude of the first signal detected by the detector is smaller than a predetermined value.