Ferrite Magnetic Material Phosphorus Doping for Demagnetization Resistance

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Solution Overview

Problem

Current ferrite magnetic materials face challenges in achieving high residual magnetic flux density (Br), coercive force (HcJ), and squareness ratio (Hk/HcJ), making it difficult to produce permanent magnets with stable magnetic properties and resistance to demagnetization due to external fields and temperature changes.

Innovation Solution

Incorporating a specific amount of phosphorus (P) into the ferrite magnetic material, with a P2O5 content of 0.001% by mass or more, which improves the Hk/HcJ ratio while maintaining sufficient Br and HcJ, and optimizing the composition with other minor constituents like Al, Cr, and B to enhance magnetic properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional ferrite magnetic materials are used, then Br and HcJ can be maintained at acceptable levels, but Hk/HcJ ratio remains low resulting in poor stability against demagnetization

Engineering Contradiction:

Improvestability against demagnetizationVSAvoiddifficulty in achieving high Br, HcJ, and Hk/HcJ simultaneously

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies parameter changes by precisely controlling the phosphorus content to be 0.001% by mass or more, which fundamentally alters the magnetic properties of the ferrite material. This specific compositional parameter change enables simultaneous achievement of high Br, HcJ, and Hk/HcJ ratio, resolving the contradiction between reliability and ease of manufacture.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite ferrite magnetic material by incorporating phosphorus as a dopant element into the ferrite structure. This composite approach, where P is added to the base ferrite material, enables improved magnetic properties including higher Hk/HcJ ratio while maintaining acceptable Br and HcJ levels.

Inventive Principle:

Principle #40Composite materials

2Reliability

If P content is increased to improve Hk/HcJ, then stability against demagnetization improves, but excessive P may adversely affect other magnetic properties

Engineering Contradiction:

ImproveHk/HcJ ratioVSAvoidadverse effect on magnetic properties

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent precisely defines the phosphorus content parameter as 0.001% by mass or more, establishing an optimal threshold that maximizes Hk/HcJ ratio while preventing adverse effects on other magnetic properties. This parameter optimization resolves the contradiction by identifying the critical concentration point where benefits peak before deterioration begins.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9336933B2Ferrite magnetic material

Publication Date: 2016.05.10 TDK CORP

AI summary

An object of the present invention is to provide a ferrite magnetic material which can provide a permanent magnet retaining high Br and HcJ as well as having high Hk/HcJ. The ferrite magnetic material according to a preferred embodiment is a ferrite magnetic material formed of hard ferrite, wherein a P content in terms of P2O5 is 0.001% by mass or more.