Microwave-Assisted Magnetic Recording Medium
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Solution Overview
Problem
High-density magnetic recording faces challenges in achieving thermal stability of magnetization, writing easiness, and recording density due to the 'trilemma' of magnetic recording, where decreasing particle size of ferromagnetic powders increases thermal stability but decreases coercivity and writing ease.
Innovation Solution
A coating type magnetic recording medium with a magnetic layer containing ferromagnetic powders of average sizes between 5 nm to 20 nm and a coefficient of variation in particle size distribution of 35% or lower, along with a thickness of 25.0 nm to 100.0 nm and thickness variation of 1.0 nm to 12.0 nm, optimized for microwave-assisted recording by applying a microwave magnetic field to assist magnetization reversal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the particle size of ferromagnetic powder is decreased to increase recording density, then the recording density is improved, but the thermal stability of magnetization deteriorates due to thermal fluctuation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution of ferromagnetic powder within 5 nm to 20 nm and maintaining a coefficient of variation of 35% or lower. This specific parameter range optimizes the balance between recording density and thermal stability, allowing high-density recording while preventing excessive thermal fluctuation that would occur with smaller particles
2Reliability
If the anisotropy constant Ku is increased to improve thermal stability of magnetization, then the thermal stability is improved, but the coercivity Hc increases making writing more difficult
Solution Approach 1:
The patent applies dynamics by introducing microwave magnetic fields during the recording process. The microwave field dynamically modifies the magnetic anisotropy of the ferromagnetic powder particles, temporarily reducing the effective coercivity during writing operations. This allows high-Ku materials to be written to easily during recording while maintaining high thermal stability during data storage
Solution Approach 2:
The patent changes the magnetic state parameter by applying microwave radiation at specific frequencies that resonate with the ferromagnetic powder particles. This resonance condition temporarily alters the magnetic anisotropy and coercivity parameters, enabling easy writing without compromising the inherent high Ku value needed for thermal stability
3Quantity of substance
If the particle volume V is decreased to achieve high-density recording, then the recording density is improved, but the magnetic energy KuV decreases reducing thermal stability
Solution Approach 1:
The patent resolves this contradiction by changing the relationship between particle size and magnetic properties through microwave assistance. The microwave field enables high-Ku, small-volume particles to be written to by temporarily modifying their magnetic response, thus decoupling the trade-off between particle volume and thermal stability
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
Improves writing easiness and thermal stability, enabling higher density recording while maintaining recording quality by enhancing responsiveness to microwave magnetic fields.
Implementation Method 1
a recording method of applying a microwave magnetic field from a magnetic head at the time of information recording to improve the writing easiness (microwave-assisted recording)
Implementation Method 2
the magnetic layer exhibits a ferromagnetic resonance frequency
Data Source
AI summary
A magnetic recording medium for microwave-assisted recording, including a non-magnetic support; and a magnetic layer containing a ferromagnetic powder and a binding agent, in which the ferromagnetic powder has an average particle size of 5 nm to 20 nm, and a coefficient of variation of a particle size distribution of 35% or lower, and the magnetic layer has a thickness of 25.0 nm to 100.0 nm, and a thickness variation of 1.0 nm to 12.0 nm. A magnetic recording device including a magnetic recording medium and a magnetic head for microwave-assisted recording. A manufacturing method of a magnetic recording medium having a servo pattern on a magnetic layer.