Perpendicular Magnetic Recording Medium Grain Control
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Solution Overview
Problem
In perpendicular magnetic recording media, achieving high recording density is hindered by grain size dispersion and transition noise, which is challenging due to the magnetic exchange interaction between magnetic grains, requiring innovative layer structures to improve crystal orientation and reduce noise.
Innovation Solution
A layered structure comprising a non-magnetic substrate, orientation control layer, non-magnetic buffer layer with silver and additive metals, non-magnetic seed layer with amorphous germanium grain boundaries, and a perpendicular magnetic recording layer, formed using specific sputtering processes to achieve improved crystal orientation and reduced grain size dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a granular-type recording layer is used to reduce magnetic exchange interaction between grains, then transition noise is reduced and limit bit size is reduced, but dispersion of inverse magnetic field increases causing increase of transition noise and jitter noise
Solution Approach 1:
The patent changes the physical and chemical parameters of the underlayer by controlling its crystal grain size to be 5 nm or less and using specific materials (CoCrPt alloy with L1(0)0(0) orientation). This parameter optimization allows the recording layer to achieve fine grain structure with reduced magnetic exchange interaction while the controlled grain size distribution minimizes inverse magnetic field dispersion, thereby reducing both transition noise and jitter noise
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers with different material properties: a soft magnetic underlayer with specific crystal orientation, a non-magnetic intermediate layer, and a perpendicular magnetic recording layer with granular structure. This composite approach allows each layer to contribute its optimal properties - the underlayer provides template effect for fine grains while the recording layer provides high coercivity and thermal stability, resolving the contradiction between noise reduction and bit size reduction
2Productivity
If the grain size of magnetic crystal grains is reduced to increase recording density, then recording density increases, but grain size dispersion increases causing increased transition noise
Solution Approach 1:
The patent applies preliminary action by preparing an underlayer with precisely controlled fine crystal grains (5 nm or less) and specific crystal orientation before forming the recording layer. This pre-established template structure guides the nucleation and growth of magnetic grains in the recording layer, ensuring uniform fine grain distribution with minimal size dispersion, thereby achieving high recording density while maintaining low transition noise
Solution Approach 2:
The patent applies local quality by creating a non-magnetic intermediate layer between the underlayer and recording layer, and by optimizing the local crystal orientation of the underlayer. This localized structural control ensures that each region of the recording layer develops uniform grain structure with consistent size, reducing grain size dispersion and transition noise while maintaining high recording density throughout the medium
3Manufacturing precision
If a non-magnetic seed layer is used to fine the grains of the recording layer, then grain size is reduced, but crystal orientation dispersion increases
Solution Approach 1:
The patent changes the approach from using a non-magnetic seed layer to directly controlling the crystal grain size of the underlayer itself to be 5 nm or less. By optimizing the underlayer's material composition (CoCrPt alloy) and crystal structure (L1(0)0(0) orientation), the patent achieves fine grain template effect while maintaining excellent crystal orientation stability, eliminating the need for separate non-magnetic seed layers and avoiding orientation dispersion
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 structure effectively reduces medium noise, maintains excellent crystal orientation, and enhances recording and reproducing characteristics by transferring the grain structure from the seed layer to the recording layer, resulting in improved recording density and thermal decay resistance.
Implementation Method 1
formed using specific sputtering processes to achieve improved crystal orientation and reduced grain size dispersion
Implementation Method 2
non-magnetic seed layer with amorphous germanium grain boundaries, and a perpendicular magnetic recording layer, formed using specific sputtering processes to achieve improved crystal orientation and reduced grain size dispersion
Data Source
AI summary
According to one embodiment, provided is a perpendicular magnetic recording medium including an orientation control layer formed on a non-magnetic substrate, the orientation control layer consisting of a Ni alloy having fcc structure, non-magnetic buffer layer containing silver having fcc structure, non-magnetic seed layer consisting of Ag particles having fcc structure and amorphous Ge grain boundaries between the Ag particles, non-magnetic intermediate layer consisting of Ru or Ru alloy, and perpendicular magnetic recording layer, wherein the orientation control layer contacts the non-magnetic buffer layer, and the non-magnetic buffer layer contacts the non-magnetic seed layer.