Strontium Ferrite Powder Surface Composition for Magnetic Recording
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Solution Overview
Problem
The development of a plate-shaped hexagonal strontium ferrite powder for magnetic recording media that simultaneously achieves excellent electromagnetic conversion characteristics and running durability has proven challenging, as existing powders struggle to balance these properties effectively.
Innovation Solution
A ferromagnetic powder with a specific composition and structure, characterized by an activation volume of 800 nm3 to 1,500 nm3, an average plate ratio of 2.0 to 5.0, rare earth atom content of 0.5 to 5.0 atom %, and aluminum atom content greater than 10.0 to 20.0 atom %, along with uneven distributions of rare earth and aluminum atoms on the surface, is developed to enhance magnetic recording medium performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If plate-shaped hexagonal strontium ferrite powder is used to improve electromagnetic conversion characteristics, then reproducing output increases, but running durability deteriorates due to surface chipping
Solution Approach 1:
The invention applies local quality by creating a surface layer with different composition than the bulk material. The surface layer has modified Al and rare earth atom concentrations specifically at the particle surfaces, while the interior maintains the base composition. This localized compositional differentiation allows the surface to provide enhanced durability while the bulk maintains high magnetization for reproducing output.
Solution Approach 2:
The invention creates a composite structure at the micro-scale where the particle consists of a bulk hexagonal strontium ferrite material with a surface layer having different atomic composition. This composite approach combines the high magnetization properties of strontium ferrite with a surface layer engineered for improved mechanical durability, resolving the contradiction between reproducing output and running durability.
2Manufacturing precision
If activation volume is reduced to improve recording density, then electromagnetic conversion characteristics improve, but thermal fluctuation increases
Solution Approach 1:
The invention applies parameter changes by precisely controlling the activation volume within a specific range (800-1500 nm³) and adjusting the atomic composition parameters (Al content 10-20 atom%, rare earth content 0.5-5.0 atom%). These parameter optimizations allow the particles to maintain stable magnetic properties while achieving high recording density, balancing electromagnetic conversion characteristics with thermal stability.
Data Source
AI summary
Provided is a ferromagnetic powder for magnetic recording, in which an activation volume is 800 nm3 to 1,500 nm3, an average plate ratio is 2.0 to 5.0, a rare earth atom content is 0.5 atom % to 5.0 atom %, and an aluminum atom content is greater than 10.0 atom % and equal to or smaller than 20.0 atom %, with respect to 100 atom % of iron atom, and the ferromagnetic powder is a plate-shaped hexagonal strontium ferrite powder having a rare earth atom surface layer portion uneven distribution and an aluminum atom surface layer portion uneven distribution, and a magnetic recording medium including this ferromagnetic powder for magnetic recording in a magnetic layer.