Epsilon Iron Oxide Recording via Light-Assisted Magnetization Inversion

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Solution Overview

Problem

Magnetic recording media with high coercive force epsilon iron oxide particles require high external magnetic fields for recording, which is challenging due to the limited saturated magnetic flux density of current hard disk materials, making it difficult to record and reproduce information effectively.

Innovation Solution

A method involving the application of an external magnetic field and light irradiation to invert the magnetization of epsilon iron oxide particles in a magnetic recording medium, reducing the required external magnetic field strength and enabling multi-valued information recording and high-speed response elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If epsilon iron oxide particles with high coercive force (Hc > 20 kOe) are used to achieve small particle volume and high thermal stability, then thermal stability of magnetization is improved, but it becomes difficult to record information due to the need for extremely high external magnetic fields that current magnetic heads cannot generate

Engineering Contradiction:

Improvethermal stability of magnetizationVSAvoidease of recording information

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent introduces a light irradiation unit as an intermediary to assist the magnetic head in inverting magnetization. The light irradiation provides additional energy to help overcome the high coercive force barrier, enabling magnetization inversion at lower magnetic field strengths that current magnetic heads can generate, thus resolving the contradiction between thermal stability and ease of recording

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the operational parameters by combining light irradiation with magnetic field application. This multi-parameter approach allows the system to achieve magnetization inversion using lower magnetic field strengths while maintaining the high thermal stability provided by the high coercive force particles

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the coercive force of the magnetic recording medium is increased to achieve high thermal stability, then thermal stability is improved, but the saturated magnetic flux density required for the magnetic head becomes unattainable with current materials

Engineering Contradiction:

Improvethermal stabilityVSAvoidmagnetic head material requirements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The light irradiation unit serves as a mediator that reduces the burden on the magnetic head. By providing optical energy assistance, the system achieves the required magnetization inversion without needing a magnetic head with unattainably high saturated magnetic flux density

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent partially replaces the purely magnetic mechanism with an optical mechanism. Instead of relying solely on high magnetic field strength from the magnetic head, the system uses light irradiation to assist in magnetization inversion, reducing the requirements for magnetic head material performance

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 allows for easy recording and reproduction of information in a low external magnetic field, even with high coercive force epsilon iron oxide particles, and facilitates a novel high-speed response element with epsilon iron oxide particles responding to terahertz light.

Implementation Method 1

performing application of an external magnetic field and irradiation of light to a magnetic recording medium using epsilon iron oxide particles as a magnetic recording material to invert magnetization of the epsilon iron oxide particles

Methodology Applied

Scientific EffectLight-induced magnetization inversion: Magneto-Optic Effects

Data Source

PatentUS11315595B2Recording method, recording device, reproduction method, reproduction device, and high-speed response element

Publication Date: 2022.04.26 FUJIFILM CORP

AI summary

The present invention provides a recording method and a recording device in which information can be easily recorded even in a magnetic recording medium using epsilon iron oxide particles having a high coercive force as a magnetic recording material. A recording device of the invention applies an external magnetic field H0 that inclines magnetization of epsilon iron oxide particles to a particle dispersion element containing epsilon iron oxide particles, and irradiates the particle dispersion element with light that excites the magnetization. Accordingly, the recording device is capable of inverting magnetization that is not capable of being inverted only by the external magnetic field, in accordance with a synergetic effect between the inclination of the magnetization and the light excitation of the magnetization.