Dynamic Spring Media With Exchange Coupled Composite Layers

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Solution Overview

Problem

Conventional perpendicular magnetic recording media with high magnetic anisotropy requires a stronger writing field, which exceeds the limit of conventional recording heads, making it difficult to record data effectively, especially with smaller grain sizes needed for increased areal density.

Innovation Solution

A multiple exchange coupled composite (ECC) structure is implemented with soft magnetic layers on both sides of hard magnetic layers, along with exchange coupling layers to provide dual magnetic torque, reducing the writing field required and enabling epitaxial texture transfer, allowing for smaller grain sizes without sacrificing recordability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If media with higher magnetic anisotropy is used to maintain thermal stability in smaller grains, then thermal stability is improved, but a stronger writing field is required that exceeds the limit of conventional recording heads

Engineering Contradiction:

Improvethermal stabilityVSAvoidwriting field strength

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The recording layer is segmented into multiple functional layers: a hard magnetic layer for thermal stability, a soft magnetic layer for assisting switching, and an exchange coupling layer to mediate between them. This segmentation allows each layer to perform its specific function optimally without compromising the others.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses a composite magnetic structure combining hard magnetic material (for high anisotropy and thermal stability) with soft magnetic material (for low coercivity and easy switching). The exchange coupling layer binds these dissimilar materials, allowing the composite structure to achieve both thermal stability and reduced writing field requirements.

Inventive Principle:

Principle #40Composite materials

2Productivity

If grain size is reduced to increase areal density, then areal density is improved, but thermal stability deteriorates due to increased thermal fluctuations in smaller grains

Engineering Contradiction:

Improveareal densityVSAvoidthermal stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the magnetic anisotropy parameter by using high anisotropy hard magnetic material in the recording layer. This parameter change allows smaller grain sizes to maintain sufficient thermal stability, enabling increased areal density without sacrificing reliability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

By combining hard magnetic material with high anisotropy with soft magnetic material through exchange coupling, the patent creates a composite structure where the hard layer provides thermal stability for small grains while the soft layer assists in switching, thereby achieving both high areal density and maintained thermal stability.

Inventive Principle:

Principle #40Composite materials

3Force

If a single ECC layer structure is used to reduce writing field, then writing field is reduced, but the reduction is limited because magnetic torque is applied only from the top side

Engineering Contradiction:

Improvewriting fieldVSAvoidswitching assistance effectiveness

Core Design Contradiction:

ForceVSProductivity

Solution Approach 1:

The patent places soft magnetic layers on both sides of the hard magnetic recording layer, creating symmetric magnetic torque assistance from both top and bottom. This counterbalancing arrangement doubles the effective switching assistance compared to single-sided ECC structures, significantly reducing the required writing field.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The invention transitions from single-sided to double-sided magnetic torque application by adding soft magnetic layers on both sides of the hard layer. This dimensional expansion from one side to two sides of the recording layer structure doubles the available switching assistance mechanism.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 the writing field necessary to switch magnetization, enabling higher areal density and improved signal-to-noise ratio, while maintaining compatibility with conventional recording heads and enhancing switching speed and data rate.

Implementation Method 1

a composite recording layer employs a magnetic soft layer 103 to exchange couple a magnetic hard layer 101 below

Methodology Applied

Scientific EffectExchange coupling:

Implementation Method 2

the magnetic soft layer 103 will switch in presence of an external field and apply a magnetic torque to assist in the switching of the magnetic hard layer 101 below

Methodology Applied

Scientific EffectMagnetic torque:

Implementation Method 3

The exchange coupling layer 102 also enables epitaxial transfer of texture from the hard magnetic recording layer 101 to the soft magnetic recording layer 103

Methodology Applied

Scientific EffectEpitaxial transfer: Epitaxy

Data Source

PatentUS8940418B1Dynamic spring media with multiple exchange coupled hard-soft magnetic layers

Publication Date: 2015.01.27 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A perpendicular magnetic recording (PMR) media structure with multiple exchange couple composite (ECC) layer structure is described. The PMR disk structure may include multiple soft magnetic layers with intervening hard magnetic layers and in between. The interface between the soft magnetic layers and the hard magnetic layers may be separated by exchange coupled layers.