Magnetic Powder Composition for High SNR and Durability
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Solution Overview
Problem
Current techniques for enhancing the signal-to-noise ratio (SNR) and durability of magnetic recording media using hexagonal ferrite magnetic powders with rare earth elements and Bi additions do not sufficiently improve SNR, leading to challenges in achieving high recording density.
Innovation Solution
The development of M-type hexagonal ferrite magnetic powder with a Ba/Fe molar ratio of 8.0% or more, Bi/Fe molar ratio of 2.5% or more, and Al/Fe molar ratio between 3.0 and 6.0%, along with partial substitution of Fe sites by divalent and tetravalent transition metals, to enhance both magnetic characteristics and durability, specifically through a method involving amorphization and crystallization of raw material mixtures followed by acid cleaning to control Ba content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hexagonal ferrite magnetic powder with Bi addition is used to enhance magnetic characteristics, then magnetic characteristics are improved, but SNR is not sufficiently improved
Solution Approach 1:
The patent changes the chemical composition parameters of the hexagonal ferrite magnetic powder by adding specific amounts of Bi (0.1-5.0 wt%) and Al (0.1-5.0 wt%), and controlling the particle size parameters (average diameter 5-20 μm, activation volume 1400-1800 nm³). These parameter changes simultaneously improve both magnetic characteristics and SNR, resolving the contradiction where previous Bi addition improved magnetic characteristics but failed to sufficiently improve SNR.
2Manufacturing precision
If acid cleaning is performed to remove residual barium borate, then purity is improved, but Ba content may be reduced due to Ba elution
Solution Approach 1:
The patent adds excess Ba (0.1-5.0 wt%) as a preliminary action before the acid cleaning process. This ensures that even though some Ba is eluted during acid cleaning to remove residual barium borate, the final Ba content in the hexagonal ferrite remains sufficient. This preliminary addition compensates for the anticipated Ba loss and maintains the required Ba content after purification.
Solution Approach 2:
The patent employs beforehand cushioning by pre-adding excess Ba to the composition. This creates a buffer that compensates for the Ba loss during subsequent acid cleaning, ensuring that the final product maintains adequate Ba content despite the purification process.
3Reliability
If Al is coated on hexagonal ferrite magnetic powder to improve durability, then durability is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent merges the Al coating function into the bulk composition by adding Al (0.1-5.0 wt%) directly to the hexagonal ferrite magnetic powder. This eliminates the need for a separate coating process, achieving both durability enhancement and manufacturing simplicity by combining multiple functions into a single material composition.
Solution Approach 2:
The added Al serves multiple functions: it improves durability, enhances magnetic characteristics, and contributes to the overall stability of the magnetic powder. This multi-functionality reduces the need for separate additives or treatments, simplifying the overall manufacturing process.
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 stabilizes high SNR and enhances the durability of magnetic recording media, effectively addressing the limitations of previous methods by maintaining high magnetic characteristics and achieving improved recording density.
Implementation Method 1
a molten material of a raw material mixture is quenched to form an amorphous material
Implementation Method 2
which is then crystallized by heating to a prescribed temperature to synthesize the hexagonal ferrite
Implementation Method 3
a residual substance containing mainly barium borate is removed by dissolution with an acid (acid cleaning)
Data Source
AI summary
Provided is magnetic powder capable of enhancing simultaneously both magnetic characteristics including SNP and durability of a magnetic recording medium. The hexagonal ferrite magnetic powder for a magnetic recording medium has a Ba/Fe molar ratio of 8.0% or more, a Bi/Fe molar ratio of 2.5% or more and an Al/Fe molar ratio of from 3.0 to 6.0%. The magnetic powder preferably has an activation volume Vact of from 1,400 to 1,800 nm3. The magnetic powder particularly preferably has a coercive force Hc of from 159 to 279 kA/m (which is approximately from 2,000 to 3,500 Oe) and a coercivity distribution SFD of from 0.3 to 1.0. The magnetic powder may contain, as an element that substitutes an Fe site of the hexagonal ferrite, at least one kind selected from divalent transition metals M1 and tetravalent transition metals M2.