Spin Torus Oscillator Pre-Biasing for Disk Protrusion Control

Solution Overview

Problem

Conventional data storage devices face challenges in accurately controlling the spin torque oscillator (STO) bias signal to achieve optimal protrusion and prevent damage during write operations, affecting data quality and longevity.

Innovation Solution

A method involving a controlled bias signal amplitude and duration for the STO, where a first bias signal is applied to quickly protrude the STO towards the disk before a write operation, then reduced to a second amplitude to maintain the target induced protrusion during writing, with specific amplitude and time ranges to prevent overheating and ensure accurate data recording.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a high bias signal amplitude is applied to the STO to achieve quick protrusion toward the disk, then the protrusion speed is improved, but the STO may overheat and suffer damage

Engineering Contradiction:

Improveprotrusion speedVSAvoidoverheating and damage

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent applies a first bias signal with a first amplitude before the write operation to quickly protrude the STO toward the disk, then reduces to a second bias signal with a second amplitude during the write operation. This preliminary action sequence allows the STO to achieve the required protrusion position without sustained high-amplitude signaling that would cause overheating.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses different bias signal amplitudes at different time periods: a higher amplitude during a pre-positioning interval, then a lower amplitude during the write operation interval. This periodic variation in signal amplitude enables quick initial protrusion followed by stable maintenance at lower thermal stress.

Inventive Principle:

Principle #19Periodic action

2Reliability

If a low bias signal amplitude is applied to the STO to prevent overheating, then the STO longevity is improved, but the protrusion speed decreases

Engineering Contradiction:

ImproveSTO longevityVSAvoidprotrusion speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent applies a first bias signal with a first amplitude before the write operation to quickly protrude the STO toward the disk, then reduces to a second bias signal with a second amplitude during the write operation. This preliminary action sequence allows the STO to achieve the required protrusion position without sustained high-amplitude signaling that would cause overheating.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses different bias signal amplitudes at different time periods: a higher amplitude during a pre-positioning interval, then a lower amplitude during the write operation interval. This periodic variation in signal amplitude enables quick initial protrusion followed by stable maintenance at lower thermal stress.

Inventive Principle:

Principle #19Periodic action

3Ease of operation

If the bias signal amplitude is not precisely controlled, then the control simplicity is improved, but the data quality and write performance deteriorate

Engineering Contradiction:

Improvecontrol simplicityVSAvoiddata quality

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent segments the bias signal into two distinct amplitudes: a first amplitude for pre-positioning and a second amplitude for the write operation. This segmentation allows each signal level to be optimized for its specific function, achieving precise control without excessive complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the bias signal parameter (amplitude) based on the operational phase: a first amplitude before the write operation for quick protrusion, then a second amplitude during the write operation for stable performance. This parameter change enables precise control adapted to different operational requirements.

Inventive Principle:

Principle #35Parameter changes

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 ensures precise control of the STO protrusion, enhancing data quality by maintaining the optimal magnetic field strength while reducing stress on the STO, thereby improving write performance and extending its longevity.

Implementation Method 1

spin torque oscillator (STO) to apply a high frequency auxiliary magnetic field to the media

Methodology Applied

Scientific EffectSpin torque:

Implementation Method 2

a first bias signal is applied to the STO during a first interval preceding a write operation to write data to the disk, wherein the first bias signal causes the STO to protrude toward the disk

Methodology Applied

Scientific EffectElectromagnetic actuation:

Data Source

PatentUS10410656B1Data storage device pre-biasing a spin torque oscillator prior to a write operation

Publication Date: 2019.09.10 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A data storage device is disclosed comprising a head actuated over a disk, wherein the head comprises a spin torque oscillator (STO). A first bias signal is applied to the STO during a first interval preceding a write operation to write data to the disk, wherein the first bias signal causes the STO to protrude toward the disk. After the first interval, a second bias signal is applied to the STO during a second interval spanning at least part of the write operation, wherein an amplitude of the first bias signal is in the range of 1.1 to 1.5 times an amplitude of the second bias signal.