Heat-Assisted Magnetic Recording Medium Stacked Granular Structure

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Solution Overview

Problem

In heat-assisted magnetic recording, achieving a high temperature gradient in the in-plane direction of a magnetic recording layer while maintaining magnetic separation between grains is challenging, particularly with materials like silicon oxide or titanium oxide, which fail to provide sufficient thermal resistance and magnetic separation.

Innovation Solution

A stacked granular structure is employed, where the lower magnetic recording layer has a non-magnetic portion mainly composed of carbon for magnetic separation and the upper layer has a non-magnetic portion from silicon oxide, silicon nitride, or titanium nitride to increase thermal resistance, allowing for a temperature gradient of 10 K/nm or higher.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a non-magnetic portion formed from silicon oxide or titanium oxide is used to surround magnetic crystal grains, then thermal resistance is increased, but magnetic separation between grains is insufficient

Engineering Contradiction:

Improvetemperature gradientVSAvoidmagnetic separation

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent uses a composite non-magnetic portion consisting of two distinct materials: silicon oxide or titanium oxide (for thermal resistance) combined with another material (for magnetic separation). This composite structure allows simultaneous achievement of high thermal resistance for temperature gradient and adequate magnetic separation between grains.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The non-magnetic portion is designed with different local properties: one region provides thermal resistance (silicon oxide/titanium oxide) while another region provides magnetic separation. This local differentiation of material properties resolves the contradiction between thermal management and magnetic isolation requirements.

Inventive Principle:

Principle #3Local quality

2Productivity

If the size of magnetic crystal grains is reduced to improve recording density, then thermal stability of recorded magnetizations deteriorates

Engineering Contradiction:

Improverecording densityVSAvoidthermal stability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent changes the material parameters of the non-magnetic portion (using silicon oxide or titanium oxide with specific thermal and magnetic properties) to compensate for the reduced size of magnetic crystal grains. This parameter change in the surrounding material compensates for the size reduction effect, maintaining thermal stability while enabling higher recording density.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If exchange interaction between magnetic crystal grains is suppressed to solve magnetization reversal unit formation, then magnetic separation must be enhanced

Engineering Contradiction:

Improvemagnetization reversal controlVSAvoidlayer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The composite non-magnetic portion using silicon oxide or titanium oxide provides both thermal resistance and magnetic separation functions in a integrated structure, suppressing exchange interaction between grains without requiring additional complex layer structures.

Inventive Principle:

Principle #40Composite materials

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 configuration enables effective heat-assisted magnetic recording with reduced noise by maintaining magnetic separation and achieving the desired temperature gradient, enhancing recording density and stability.

Implementation Method 1

a non-magnetic portion that surrounds the magnetic crystal grains and is formed from a material mainly composed of carbon, and an upper magnetic recording layer having a granular structure including magnetic crystal grains and a non-magnetic portion that surrounds the magnetic crystal grains and is formed from a material different from that of the non-magnetic portion of the lower magnetic recording layer

Methodology Applied

Scientific EffectThermal resistance: Thermal Insulation

Implementation Method 2

A L10-based ordered alloy is proposed as a material having the required high crystalline magnetic anisotropy

Methodology Applied

Scientific EffectTemperature dependency on magnetic anisotropy constant: Anisotropy

Implementation Method 3

The individual magnetic crystal grains in the granular magnetic material are magnetically separated by the non-magnetic material

Methodology Applied

Scientific EffectMagnetic separation: Magnetism

Data Source

PatentUS9728218B2Magnetic recording medium for heat-assisted magnetic recording

Publication Date: 2017.08.08 FUJI ELECTRIC CO LTD

AI summary

A magnetic recording medium for heat-assisted magnetic recording is provided. A magnetic recording layer includes upper and lower magnetic recording layers. The lower magnetic recording layer has a lower granular structure including lower magnetic crystal grains, and a lower non-magnetic portion, that surrounds the lower magnetic crystal grains, mainly composed of carbon. The upper magnetic recording layer has an upper granular structure including upper magnetic crystal grains, and an upper non-magnetic portion, that surrounds the upper magnetic crystal grains, formed from a material selected from the group consisting of silicon nitride, titanium oxide and titanium nitride.