Magnetic Recording Underlayer Structure for Heat-Assisted Magnetic Recording

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Solution Overview

Problem

Existing heat-assisted and microwave-assisted magnetic recording technologies face challenges in achieving high recording density due to insufficient (001) orientation of magnetic layers with L10-type crystal structures, leading to suboptimal coercive force and signal-to-noise ratio (SNR) in magnetic recording media.

Innovation Solution

A magnetic recording medium is designed with a specific underlayer structure, including a first underlayer with a B2 or BCC structure containing Cr, a second underlayer with a BCC structure, and a third underlayer with a NaCl-type crystal structure, which enhances the (001) orientation of the magnetic layer, thereby improving coercive force and SNR. This structure is used in both heat-assisted and microwave-assisted magnetic recording types.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a magnetic layer with L10-type crystal structure is used to achieve high coercive force and thermal stability, then thermal stability is improved, but the (001) orientation is insufficient leading to suboptimal recording characteristics

Engineering Contradiction:

Improvethermal stabilityVSAvoid(001) orientation

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The underlayer is divided into three distinct layers (first underlayer with B2/BCC structure, second underlayer with BCC structure, third underlayer with NaCl-type structure) that work together to promote (001) orientation of the magnetic layer while maintaining thermal stability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each underlayer is designed with specific crystal structures and lattice constants to create local conditions that favor (001) orientation. The first underlayer has B2 or BCC structure with specific lattice constant, the second has BCC structure, and the third has NaCl-type structure, creating a gradient that promotes desired orientation

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If the particle size of the magnetic layer is reduced to increase recording density, then recording density is improved, but thermal stability deteriorates

Engineering Contradiction:

Improverecording densityVSAvoidthermal stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The invention changes the crystal structure parameters of the underlayer (using B2, BCC, and NaCl-type structures with specific lattice constants) to enable (001) orientation in the magnetic layer, which maintains high coercive force and thermal stability even at reduced particle sizes for higher recording density

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If high Ku materials with L10-type crystal structure are used to reduce particle volume, then thermal stability index (KuV/kT) is maintained, but the (001) orientation is insufficient leading to suboptimal coercive force and SNR

Engineering Contradiction:

Improvethermal stability index (KuV/kT)VSAvoidcoercive force and SNR

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The three-layer underlayer structure acts as an intermediary between the substrate and the magnetic layer, creating the necessary crystallographic conditions for (001) orientation. The specific sequence of B2/BCC, BCC, and NaCl-type structures mediates the orientation development in the high Ku magnetic layer

Inventive Principle:

Principle #24Intermediary (Mediator)

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 proposed structure achieves a high coercive force and signal-to-noise ratio (SNR) in magnetic recording media, enhancing recording density and reducing error rates, particularly in heat-assisted and microwave-assisted magnetic recording applications.

Implementation Method 1

the under layer includes, in order from the substrate side, a first under layer with a lattice constant a of 2.87 Å≦a<3.08 Å and having a B2 structure or a BCC structure, a second under layer with a lattice constant a of 3.04 Å≦a<3.20 Å and having a BCC structure, and a third under layer with a lattice constant a of 3.18 Å≦a

Methodology Applied

Scientific EffectCrystal structure orientation:

Data Source

PatentUS8792313B2Magnetic recording medium having multiple under layers for heat-assisted magnetic recording apparatus

Publication Date: 2014.07.29 RESONAC HARD DISK CORP

AI summary

A magnetic recording medium of the present invention includes an under layer formed on a substrate, and a magnetic layer, formed on the under layer, which contains an alloy having an L10-type crystal structure as a main component. The under layer includes, in order from the substrate side, a first under layer with a lattice constant a of 2.87 Å≦a<3.04 Å, a second under layer having a BCC structure with a lattice constant a of 3.04 Å≦a<3.18 Å, a third under layer having a BCC structure with a lattice constant a of 3.18 Å≦a<3.31 Å, and an upper under layer having a NaCl-type crystal structure. The first under layer has a B2 structure, or has a BCC structure containing Cr as a main component. In the magnetic recording medium of the present invention, information is recorded using a heat-assisted magnetic recording type, or a microwave-assisted magnetic recording type.