Servo Patterns With Selective Magnetization For Signal Symmetry

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Patterned recording media for digital data storage devices face reduced peak-to-peak amplitude and DC baseline shifts due to readback signals swinging between high and low or zero signals, rather than positive and negative signals of equal magnitude, leading to surface roughness and inefficient read-write head positioning.

Innovation Solution

Incorporating a servo pattern with two populations of magnetic features having differential magnetic properties, allowing selective magnetization to orient magnetic moments in opposite directions, thereby increasing peak-to-peak amplitude and minimizing DC baseline shifts without contributing to surface roughness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If DC magnetization is used to write servo information, then servo information can be written to the patterned recording medium, but the readback signal swings between high and low or zero signals instead of positive and negative signals of equal magnitude

Engineering Contradiction:

Improveservo information writing capabilityVSAvoidreadback signal symmetry

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The servo sector is divided into two distinct populations of magnetic features: first population features with magnetization in a first direction and second population features with magnetization in a second direction opposite to the first direction. This segmentation allows the readback signal to swing between positive and negative values of equal magnitude, resolving the signal symmetry problem while maintaining reliable servo information.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the servo sector are assigned different magnetic polarities (first population with one polarity, second population with opposite polarity). This local differentiation creates the desired bipolar readback signal pattern, where each population contributes equally but with opposite signs, achieving symmetric signal swings around zero.

Inventive Principle:

Principle #3Local quality

2Reliability

If magnetic material is removed from certain magnetic regions to create servo patterns, then servo information can be incorporated, but surface roughness is inadvertently added to the patterned recording medium

Engineering Contradiction:

Improveservo information incorporationVSAvoidsurface roughness

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Instead of removing magnetic material to create servo patterns, the invention changes the magnetization parameter of existing magnetic features. By magnetizing first and second populations of features in opposite directions within the servo sector, servo information is encoded without any material removal, thereby avoiding surface roughness while maintaining reliable servo functionality.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If readback signals swing between high and low or zero signals, then servo information can be read, but DC baseline shifts occur when the read-write head moves from servo sectors to data areas

Engineering Contradiction:

Improveservo signal readbackVSAvoidDC baseline stability

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The servo sector is segmented into two populations of magnetic features with equal but opposite magnetization directions. This creates a bipolar readback signal that is symmetric around zero, ensuring that the average (DC) component remains stable when transitioning between servo and data sectors, thereby eliminating DC baseline shifts.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second population of magnetic features acts as a counterweight to the first population, with equal magnitude but opposite direction magnetization. This counterbalancing arrangement ensures that the net DC component of the readback signal remains zero or stable, preventing baseline shifts when the read-write head moves between different sector types.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

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 solution enhances readback signal amplitude and stabilizes the servo pattern, improving read-write head positioning accuracy and reducing surface roughness, while maintaining the same or similar magnetic feature properties as data sectors.

Implementation Method 1

a selective magnetization means for selective magnetization of either one of the first population or the second population of magnetic features over the other

Methodology Applied

Scientific EffectSelective magnetization: Magnetism

Data Source

PatentUS8879184B1Servo patterns including selectively magnetizable magnetic features

Publication Date: 2014.11.04 SEAGATE TECH LLC

AI summary

Provided herein is an apparatus, including a servo pattern having magnetic features, wherein each magnetic feature of the magnetic features includes a single magnetic domain; a first population of the magnetic features; a second population of the magnetic features; and a selective magnetization means for selective magnetization of either one of the first population or the second population of magnetic features over the other.